Immunization of Children under 2 Years Old in the Coastal Hadhramaut Governorate, Yemen, during Public Health Emergencies: A Trend Analysis of 2013–2020

Abstract

Although immunization is one of the most successful and cost-effective interventions that prevents millions of infant and child deaths yearly, it has failed to achieve its intended goals in some low-income countries. Yemen is currently experiencing the most extreme humanitarian crisis globally, which has affected health and worsened its economy and political governance instability. There are few reports on Yemeni vaccination statuses. The present study aimed to investigate the effect of the public health emergency crises on childhood immunization in Yemen. A retrospective descriptive study was conducted in the Coastal Hadhramaut Governorate, Yemen. Secondary data from governorate annual reports for 2013–2020 were extracted. The assessment of the annual immunization coverage rate according to each vaccine was tabulated. The analysis revealed that the 2013–2019 vaccination coverage in Coastal Hadhramaut demonstrated an increasing trend. However, vaccination coverage decreased for all vaccines in 2015–2016 and 2020. Although all three doses of the pentavalent vaccine demonstrated >85% coverage in all years, the coverage of the first and second doses decreased in 2016, and the coverage of all doses decreased in 2020 during the COVID-19 pandemic. Public health emergencies negatively affected routine immunization coverage in Yemen. The trend correlated with the humanitarian crisis and other research findings in Yemen. The national response to public health threats during emergency crises must involve strengthening the program for monitoring and evaluating vaccine-preventable diseases.

Full text

Citation: Batarfi, S.A.; Sutan, R.;
Ismail, H.; Bin-Ghouth, A.S.
Immunization of Children under 2
Years Old in the Coastal Hadhramaut
Governorate, Yemen, during Public
Health Emergencies: A Trend
Analysis of 2013–2020. Vaccines 2024,
12, 311. https://doi.org/10.3390/
vaccines12030311
Academic Editor: Christian Napoli
Received: 18 December 2023
Revised: 8 March 2024
Accepted: 11 March 2024
Published: 15 March 2024
Copyright: © 2024 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
Article
Immunization of Children under 2 Years Old in the Coastal
Hadhramaut Governorate, Yemen, during Public Health
Emergencies: A Trend Analysis of 2013–2020
Suha Ali Batarfi 1, 2, *, Rosnah Sutan 1, * , Halim Ismail 1and Abdulla Salem Bin-Ghouth 2
1Department of Public Health Medicine, Medical Faculty, Universiti Kebangsaan Malaysia,
Kuala Lumpur 56000, Malaysia
2Community Medicine Department, Hadhramout University College of Medicine and Health Sciences,
Al Mukalla 10587, Yemen
*Correspondence: batarfisuhaali@gmail.com (S.A.B.); rosnah_sutan@yahoo.com (R.S.);
Tel.: +60-1127107155 (S.A.B.); +603-91459587 (R.S.)
Abstract:
Although immunization is one of the most successful and cost-effective interventions that
prevents millions of infant and child deaths yearly, it has failed to achieve its intended goals in
some low-income countries. Yemen is currently experiencing the most extreme humanitarian crisis
globally, which has affected health and worsened its economy and political governance instability.
There are few reports on Yemeni vaccination statuses. The present study aimed to investigate the
effect of the public health emergency crises on childhood immunization in Yemen. A retrospective
descriptive study was conducted in the Coastal Hadhramaut Governorate, Yemen. Secondary
data from governorate annual reports for 2013–2020 were extracted. The assessment of the annual
immunization coverage rate according to each vaccine was tabulated. The analysis revealed that the
2013–2019 vaccination coverage in Coastal Hadhramaut demonstrated an increasing trend. However,
vaccination coverage decreased for all vaccines in 2015–2016 and 2020. Although all three doses
of the pentavalent vaccine demonstrated >85% coverage in all years, the coverage of the first and
second doses decreased in 2016, and the coverage of all doses decreased in 2020 during the COVID-19
pandemic. Public health emergencies negatively affected routine immunization coverage in Yemen.
The trend correlated with the humanitarian crisis and other research findings in Yemen. The national
response to public health threats during emergency crises must involve strengthening the program
for monitoring and evaluating vaccine-preventable diseases.
Keywords: childhood immunization; pandemic; crisis; preparedness plan; Yemen
1. Introduction
Primary prevention through vaccination programs is one of the most effective and
cost-efficient means of preventing infant and child deaths. However, limited access and
funding for vaccine programs affect its implementation, as was seen in some underserved
populations where vaccine programs failed to reach the intended goals [
1
]. Each year,
vaccination averts an estimated 2–3 million child deaths from vaccine-preventable diseases
(VPDs) [
2
]. Vaccination is vital to attain Sustainable Development Goal (SDG) objectives,
specifically SDG 3 (Good Health and Well-being). It has a broader reach than any other
healthcare or social service, forming the cornerstone of primary healthcare systems and
serving as a significant method for achieving universal health coverage [3].
Yemen is a low-income Arab nation with an unstable healthcare system and poor
socioeconomic conditions. Yemen comprises 22 governorates over 333 districts. The largest
governorate in Yemen is Hadhramaut, which is affected by the internal displacement of
residents from other governorates [
4
]. The Expanded Program of Immunization (EPI)
in Yemen was initiated in 1979 to reduce morbidity and mortality associated with VPDs.
Vaccines 2024,12, 311. https://doi.org/10.3390/vaccines12030311 https://www.mdpi.com/journal/vaccines

Vaccines 2024,12, 311 2 of 13
The EPI targets children under 1 year old, pregnant women, and women of reproductive
age [
5
]. Childhood vaccination coverage in Yemen improved significantly since the EPI
began. However, the most recent Yemen National Health and Demographic Survey in 2013
reported that only 42.6% of children aged 12–23 months were fully vaccinated, while 16%
did not receive any vaccination [6].
Nevertheless, coverage gaps persist between regions, countries, and within countries.
The World Health Organization (WHO) estimated that approximately 17% of infants world-
wide (22.7 million infants) did not receive the diphtheria, tetanus, and pertussis (DTP)
vaccine in 2020 [
1
,
7
]. Routine vaccination coverage in several WHO Eastern Mediterranean
Region (EMRO) countries markedly improved during the past two decades. However, vac-
cination declined in some countries (Yemen, Syria, and Iraq) due to prevailing geopolitical
circumstances, which decreased regional DTP dose 3 (DTP3) coverage from 85% (2010) to
80% (2016) [
8
]. Furthermore, Southeast Asia and the EMRO recorded the largest decline
in DTP3 coverage in 2020 [
8
]. The United Nations Children’s Fund (UNICEF) and WHO
reported that the vaccination coverage for Yemen in 2018 was 65% based on DTP3, which
remained below the 90% that every country should have achieved by 2020 [9].
Disasters, both natural and human-made, are increasing worldwide and have serious
consequences for humanity and economies [
10
]. Children and adolescents are the most
vulnerable groups affected by the consequences of disasters [
11
]. Thus, all countries should
establish and maintain a preparedness plan to overcome such emergencies. Although many
health interventions and research priorities have been published for reference, studies in
the Middle East indicated that this topic requires much work [
12
]. Yemen has been exposed
to many natural and man-made disasters in the past decade, such as earthquakes, cyclones,
flooding, internal conflict, civil war, and pandemics [
13
]. It has experienced conflict since
2011, when anti-government protests began. In March 2015, the ongoing Yemen civil war
began when Houthi rebels, a Shi’a group, seized control of the Yemeni capital, Sana’a [
4
,
14
].
Both the conflict and civil war negatively affected the national infrastructure and
resulted in further political and social instability. Millions of people were displaced from
their homes and often faced challenges accessing healthcare services, including basic
child immunization [
15
]. More than 50% of Yemeni health facilities are currently unable
to provide healthcare services following the crisis [
16
]. The risk of violence and fear of
attacks prevented families from accessing healthcare, including immunization services.
Disruptions to the vaccine supply chain, damage to cold-storage facilities, and limited
access to remote areas also contributed to the decreased vaccination coverage in Yemen [
17
].
Thus, the constant conflict in Yemen has caused a widespread humanitarian catastrophe
and destroyed an already fragile health system [18].
The COVID-19 pandemic had broad effects and affected most aspects of human
life. The pandemic affected health system management because of staffing deployment
to control the pandemic, and disrupted the delivery of most health services following
movement restriction orders, including immunization [
19
]. Furthermore, the pandemic
affected routine vaccination globally, where the coverage of DTP3 and the polio vaccine
decreased from 86% in 2019 to 83% in 2020. This decrease led to the largest number
of unvaccinated children since 2009 (22.7 million), an increase of 3.7 million from 2019.
Additionally, the global coverage of the first dose of measles-containing vaccine (MCV1)
decreased from 86% in 2019 to 84% in 2020 [
7
]. Several studies addressed the effect of the
pandemic on child health globally, especially childhood vaccination, and confirmed the
decline in routine vaccination coverage in children in numerous countries, especially in
low- and middle-income countries (LMICs) [20].
Yemen was weakened due to the ongoing civil war, and the COVID-19 pandemic
exacerbated the situation [
21
,
22
]. Yemen faces a complex multifaceted situation; the war
and the pandemic have significantly affected the achievement of SDG 3 and other SDGs,
such as SDG 1 (No Poverty), SDG 2 (Zero Hunger), and SDG 6 (Clean Water and Sanitation).
Figure 1illustrates the main conflict events and health issues in 2011–2020 that influenced
the deterioration of health facilities and services.

Vaccines 2024,12, 311 3 of 13
Vaccines 2024, 12, x FOR PEER REVIEW 3 of 14
such as SDG 1 (No Poverty), SDG 2 (Zero Hunger), and SDG 6 (Clean Water and Sanita-
tion). Figure 1 illustrates the main conflict events and health issues in 2011–2020 that in-
fluenced the deterioration of health facilities and services.
Figure 1. Milestones of main conflict events and their relationship with health issues in Yemen in
2011–2020.
Studying routine immunization trends can reveal vital insights and inform and aid
EPI stakeholders in developing plans to minimize the number of unvaccinated children
who dropped out of the EPI during the Yemen crisis [23]. Only one study, by Torbosh et
al. [14], was conducted to assess the one-year impact of war on childhood immunization
in Yemen. To the best of our knowledge, no other published studies address the effect of
a public health crisis (e.g., continuous war and pandemic) in Yemen. Therefore, this study
intends to address the issue of child immunization coverage by analyzing the child im-
munization coverage trend in Hadhramaut Governorate, Yemen, during the emergency
crisis (especially the war and the COVID-19 pandemic) in 2013–2020.
2. Materials and Methods
2.1. Study Design and Seing
This paper is part (phase 1) of 3 phases of a mixed-method study exploring parental
vaccine hesitancy and childhood vaccination in coastal Hadhramaut, Yemen. The protocol
of the methodology has already been published [5]. For the phase 1 study, a retrospective
descriptive study was performed with wrien permission to use secondary data obtained
from the Coastal Hadhramaut Health and Population Affairs Office in 2021, after being
granted ethic approval on 18th February 2021. The study focused on Hadhramaut Gover-
norate as it is the largest governorate in Yemen and the one most affected by war-displaced
people. The Hadhramaut Governorate administration is divided into the valley/desert
(Wadi Hadhramaut) and coast (Coastal Hadhramaut) (Figure 2) [24]. This study focused
on Coastal Hadhramaut, which consists of 12 districts: Al-Mukalla, Al-Dees, Al-Shahr, Al-
dulaia, Broome-Mayfa’a, Doan, Gail Bawazeer, Ghail bin Yumin, Hajer, Ridh and Gosaiar,
rural Al-Mukalla, and Yeabeth. Coastal Hadhramaut overlooks the Arabian Sea to the
south and has approximately 120 km of coastline. An estimated 994,771 people lived in
Coastal Hadhramaut in 2021, and the yearly population growth rate is 3.02% [25].
Figure 1.
Milestones of main conflict events and their relationship with health issues in Yemen in
2011–2020.
Studying routine immunization trends can reveal vital insights and inform and aid
EPI stakeholders in developing plans to minimize the number of unvaccinated children
who dropped out of the EPI during the Yemen crisis [
23
]. Only one study, by Torbosh
et al. [
14
], was conducted to assess the one-year impact of war on childhood immunization
in Yemen. To the best of our knowledge, no other published studies address the effect
of a public health crisis (e.g., continuous war and pandemic) in Yemen. Therefore, this
study intends to address the issue of child immunization coverage by analyzing the child
immunization coverage trend in Hadhramaut Governorate, Yemen, during the emergency
crisis (especially the war and the COVID-19 pandemic) in 2013–2020.
2. Materials and Methods
2.1. Study Design and Setting
This paper is part (phase 1) of 3 phases of a mixed-method study exploring parental
vaccine hesitancy and childhood vaccination in coastal Hadhramaut, Yemen. The protocol
of the methodology has already been published [
5
]. For the phase 1 study, a retrospective
descriptive study was performed with written permission to use secondary data obtained
from the Coastal Hadhramaut Health and Population Affairs Office in 2021, after being
granted ethic approval on 18th February 2021. The study focused on Hadhramaut Gover-
norate as it is the largest governorate in Yemen and the one most affected by war-displaced
people. The Hadhramaut Governorate administration is divided into the valley/desert
(Wadi Hadhramaut) and coast (Coastal Hadhramaut) (Figure 2) [
24
]. This study focused
on Coastal Hadhramaut, which consists of 12 districts: Al-Mukalla, Al-Dees, Al-Shahr,
Al-dulaia, Broome-Mayfa’a, Doan, Gail Bawazeer, Ghail bin Yumin, Hajer, Ridh and Gosa-
iar, rural Al-Mukalla, and Yeabeth. Coastal Hadhramaut overlooks the Arabian Sea to the
south and has approximately 120 km of coastline. An estimated 994,771 people lived in
Coastal Hadhramaut in 2021, and the yearly population growth rate is 3.02% [25].

Vaccines 2024,12, 311 4 of 13
Vaccines 2024, 12, x FOR PEER REVIEW 4 of 14
Figure 2. Map of Yemen. Source: Free Map Viewer. [24].
2.2. Vaccination Process in Yemen
Following EPI initiation in 1979, routine immunization services in Yemen are offered
for free through fixed vaccination posts in health facilities (health centers or units) and an
outreach vaccination strategy depending on the resident’s proximity to the facility. Ini-
tially, the EPI aimed to reduce child mortality and morbidity for 6 VPDs and later ex-
panded to cover 11 VPDs (tuberculosis, poliomyelitis, diphtheria, pertussis, tetanus, hep-
atitis B, pneumococcal infections, meningitis, rotavirus diarrheal diseases, measles, and
rubella). The WHO recommended that the EPI strategy is to achieve no less than 90%
vaccination coverage nationally and at least 80% at the governorate level. In the Coastal
Hadhramaut Governorate, 166 governmental health facilities provide immunization ser-
vices, which are insufficient to meet the population’s basic needs, especially with the in-
flux of people displaced from nearby districts [26]. The high fertility rate in Yemen con-
tributes to high service demands with a limited healthcare staffing ratio [25].
Vaccination documentation is routinely charted daily at the health facilities using
tally sheet forms and routine vaccination registration records. The data from each health
facility are compiled monthly and forwarded to the district immunization manager, who
collates and summarizes them as a monthly district immunization report. Subsequently,
the 12 districts deliver their monthly district immunization reports to the Department of
EPI in the Health and Population Affairs Office—Coastal Hadhramaut. Later, the data are
entered into an Excel sheet for analysis and grouped to compile the data for the gover-
norate. Then, the compilation is delivered to the Department of EPI at the Ministry of
Public Health and Population to be reported as an annual report [5,26].
2.3. Data Collection and Analysis
The present study collected secondary data via soft-copy annual reports and availa-
ble data in Excel format from 2013 to 2020. The researcher rechecked the data by examin-
ing a hard copy of each district immunization report to ensure that the data were valid.
The researcher ensured that there were no missing data and no data entry errors, and that
Figure 2. Map of Yemen. Source: Free Map Viewer. [24].
2.2. Vaccination Process in Yemen
Following EPI initiation in 1979, routine immunization services in Yemen are offered
for free through fixed vaccination posts in health facilities (health centers or units) and an
outreach vaccination strategy depending on the resident’s proximity to the facility. Initially,
the EPI aimed to reduce child mortality and morbidity for 6 VPDs and later expanded
to cover 11 VPDs (tuberculosis, poliomyelitis, diphtheria, pertussis, tetanus, hepatitis B,
pneumococcal infections, meningitis, rotavirus diarrheal diseases, measles, and rubella).
The WHO recommended that the EPI strategy is to achieve no less than 90% vaccination
coverage nationally and at least 80% at the governorate level. In the Coastal Hadhramaut
Governorate, 166 governmental health facilities provide immunization services, which
are insufficient to meet the population’s basic needs, especially with the influx of people
displaced from nearby districts [
26
]. The high fertility rate in Yemen contributes to high
service demands with a limited healthcare staffing ratio [25].
Vaccination documentation is routinely charted daily at the health facilities using
tally sheet forms and routine vaccination registration records. The data from each health
facility are compiled monthly and forwarded to the district immunization manager, who
collates and summarizes them as a monthly district immunization report. Subsequently, the
12 districts
deliver their monthly district immunization reports to the Department of EPI in
the Health and Population Affairs Office—Coastal Hadhramaut. Later, the data are entered
into an Excel sheet for analysis and grouped to compile the data for the governorate. Then,
the compilation is delivered to the Department of EPI at the Ministry of Public Health and
Population to be reported as an annual report [5,26].
2.3. Data Collection and Analysis
The present study collected secondary data via soft-copy annual reports and available
data in Excel format from 2013 to 2020. The researcher rechecked the data by examining
a hard copy of each district immunization report to ensure that the data were valid. The

Vaccines 2024,12, 311 5 of 13
researcher ensured that there were no missing data and no data entry errors, and that the
district report data matched the Excel data. A trend analysis was conducted by assessing
the yearly vaccination coverage for each vaccine type by district (for multidose vaccines,
the coverage rate for each dose was estimated). The WHO defines vaccination coverage as
“the proportion of a given population that has been vaccinated in a given period” [
27
]. The
vaccination coverage rate (mostly expressed as a percentage) was calculated by dividing
the total number of children who received a specific vaccine during the reporting year (the
numerator) by the target population during that year (the denominator) and multiplying
the result by 100 [
26
]. The EPI data use the population projection for the current years
based on 2004 census data as there are no available census data since then. The internal
displacement of people from the neighboring Governorates during the war has caused the
vaccination coverage to be slightly more than 100%. The factors contributing to coverage of
more than 100% were due to reporting errors that resulted from the population estimate
being lower than the actual population’s current size and temporary population increases
due to the presence of internal migration. Capping vaccination coverage at 100% is carried
out for reporting in the present study to prevent misunderstanding on data interpretation
with a coverage of more than 100%. Table 1presents the routine immunization schedule, as
presented in the analysis: one dose of bacillus Calmette-Guérin (BCG); doses 1–3 of the oral
polio vaccine (OPV), the pneumococcal conjugate vaccine (PCV), and a pentavalent vaccine
that protects against diphtheria, tetanus, pertussis, hepatitis B, and Hemophilus influenzae
type B (Hib); doses 1 and 2 of the measles-rubella combination vaccine (MR); doses 1 and 2
of the rotavirus vaccine; and one dose of the inactivated poliovirus vaccine (IPV).
Table 1. Routine immunization schedule for children in Yemen.
Age of the Child Vaccine Remarks
After birth BCG (single dose), OPV BCG (essential dose)
OPV (non-essential dose)
6 weeks OPV dose 1, pentavalent vaccine, PCV, rotavirus vaccine Administer BCG if not administered previously
10 weeks OPV dose 2, pentavalent vaccine, PCV, rotavirus vaccine The minimum interval between doses 1 and 2 is 4 weeks
14 weeks OPV dose 3, pentavalent vaccine, PCV, IPV The minimum interval between doses 2 and 3 is 4 weeks
9 months
MR dose 1 + vitamin A (100 UI) + OPV (non-essential dose)
The minimum age is 9 months
18 months
MR dose 2 + vitamin A (200 UI) + OPV (non-essential dose)
The minimum age is 18 months
2.4. Ethical Consideration
Ethical approval was obtained, and the Coastal Hadhramaut Health and Population
Affairs Office general manager granted written permission to use the EPI department
data. The Research Ethics Committee of the Faculty of Medicine, Universiti Kebangsaan
Malaysia, granted ethical approval (project code: FF-2021-051).
3. Results
Anonymous data obtained from the EPI department were recorded according to
vaccination type and year. Data from 2013 to 2020 in Excel format were obtained together
with the hard copy of each district immunization report. The researcher verified the data
for completeness and validity. There were no data entry errors, no missing data, and the
same data for each district were available in both hard- and soft-copy formats. The annual
reports presented the vaccination coverage for each Coastal Hadhramaut district.
Generally, Coastal Hadhramaut vaccination coverage increased for most vaccines from
2013 to 2019 (Figures 3and 4). However, vaccination coverage decreased for all vaccines in
2020. Furthermore, BCG, MR, and rotavirus vaccine coverage decreased in 2015–2016 in
addition to the decrease in 2020.

Vaccines 2024,12, 311 6 of 13
Vaccines 2024, 12, x FOR PEER REVIEW 6 of 14
vaccines in 2020. Furthermore, BCG, MR, and rotavirus vaccine coverage decreased in
2015–2016 in addition to the decrease in 2020.
Figure 3. Vaccination coverage of single-dose vaccines (BCG (a) and IPV (b)) in Coastal
Hadhramaut in 2013–2020.
3.1. BCG Vaccine Coverage
The BCG vaccine is administered immediately after birth and is the first vaccine type
administered in Yemen. Most children receive the BCG vaccine at birth. At the age of 6
weeks, children receive OPV dose 1, the pentavalent and pneumococcal vaccines. BCG
vaccine coverage in Coastal Hadhramaut decreased slightly in 2014, with a marked de-
crease in 2015 (−11%) (Figure 3a). Subsequently, BCG vaccine coverage began to increase
from 2016 to 2019. In 2020, BCG coverage decreased (−15%) compared to 2019. The district-
level analysis revealed a similar increasing trend in BCG vaccine coverage until 2020 when
the coverage began to decrease. Decreased BCG coverage occurred in most districts in
2015 (Supplementary Materials: Table S1). The Al-Mukalla district demonstrated persis-
tently high BCG vaccine coverage for all years (>80%), while rural Al-Mukalla, Doan, Al-
Dulaia, Hajer, and Yeabeth demonstrated persistently low coverage for all years (<80%).
The other districts demonstrated varied BCG vaccine coverage, where most had good cov-
erage after 2015.
3.2. IPV Coverage
IPV was introduced to the routine immunization program in Yemen at the end of
2015 and is administered to children in one dose at the age of 14 weeks [6]. As with other
Figure 3.
Vaccination coverage of single-dose vaccines (BCG (
a
) and IPV (
b
)) in Coastal Hadhramaut
in 2013–2020.
3.1. BCG Vaccine Coverage
The BCG vaccine is administered immediately after birth and is the first vaccine
type administered in Yemen. Most children receive the BCG vaccine at birth. At the age
of 6 weeks, children receive OPV dose 1, the pentavalent and pneumococcal vaccines.
BCG vaccine coverage in Coastal Hadhramaut decreased slightly in 2014, with a marked
decrease in 2015 (
−
11%) (Figure 3a). Subsequently, BCG vaccine coverage began to
increase from 2016 to 2019. In 2020, BCG coverage decreased (
−
15%) compared to
2019. The district-level analysis revealed a similar increasing trend in BCG vaccine
coverage until 2020 when the coverage began to decrease. Decreased BCG coverage
occurred in most districts in 2015 (Supplementary Materials: Table S1). The Al-Mukalla
district demonstrated persistently high BCG vaccine coverage for all years (>80%), while
rural Al-Mukalla, Doan, Al-Dulaia, Hajer, and Yeabeth demonstrated persistently low
coverage for all years (<80%). The other districts demonstrated varied BCG vaccine
coverage, where most had good coverage after 2015.

Vaccines 2024,12, 311 7 of 13
Vaccines 2024, 12, x FOR PEER REVIEW 8 of 14
Figure 4. Vaccination coverage of multidose vaccines (MR (a), rotavirus (b), and pentavalent (c)) in
Coastal Hadhramaut in 2013–2020.
Figure 4.
Vaccination coverage of multidose vaccines (MR (
a
), rotavirus (
b
), and pentavalent (
c
)) in
Coastal Hadhramaut in 2013–2020.
3.2. IPV Coverage
IPV was introduced to the routine immunization program in Yemen at the end of
2015 and is administered to children in one dose at the age of 14 weeks [
6
]. As with
other vaccines, IPV coverage increased in Coastal Hadhramaut until 2020, before it sharply

Vaccines 2024,12, 311 8 of 13
decreased (
−
14%) (Figure 3b). District-level analysis revealed that all districts demonstrated
decreased coverage in 2020. The Al-Mukalla, Ridh and Gosaiar, Ghail Bawazeer, and
Ghail bin Yumin districts exhibited persistently good coverage, while the Al-Dees, Doan,
Al-Dulaia, and Yeabeth districts exhibited constantly low IPV coverage (Supplementary
Materials: Table S2).
3.3. MR Vaccine Coverage
Yemeni children receive MR vaccine dose 1 (MR1) at 9 months of age, and dose 2
at 18 months. In 2014, the coverage of both doses 1 and 2 of the MR vaccine in Coastal
Hadhramaut decreased (
−
5%) as compared to 2013 (Figure 4a). Another decline was
recorded in 2016 and 2017 for both doses. Subsequently, vaccine coverage increased over
time until 2019, when the coverage of both doses began to decrease in 2020 (Figure 4a).
District-level analysis revealed that despite the increased MR1 coverage over the
years, most districts exhibited low vaccine coverage in 2020, and only four districts had
coverage > 80% (Al-Mukalla, Ghail Bawazeer, Ghail bin Yumin, and Yeabeth). Al-Dulaia
and Hajer demonstrated persistently low coverage of MR1 for all years, while other districts
demonstrated varied coverage, with low coverage in some years and good coverage
in later years. However, MR2 coverage was persistently low in all districts over time
(Tables S3 and S4).
3.4. Rotavirus Vaccine Coverage
Yemeni children receive two doses of the rotavirus vaccine. Doses 1 and 2 are ad-
ministered when the child is 6 and 10 weeks old, respectively. Although the coverage
of both rotavirus vaccine doses increased over time in Coastal Hadhramaut, coverage in
2016 decreased by 5% compared to 2015 and decreased by 9% in 2020 compared to 2019
(Figure 4b). The district-level analysis revealed that the coverage of both doses of the
rotavirus vaccine increased over time. Nevertheless, most districts had <80% coverage
between 2013 and 2016, except Al-Mukalla district, which had persistently good coverage
(>80%) in all years (2013–2020). After 2016, all districts demonstrated increased vaccine
coverage, where most had >80% coverage (Tables S5 and S6).
3.5. OPV, Pentavalent, and Pneumococcal Vaccine Coverage
The Yemen EPI schedule states that doses 1, 2, and 3 of the OPV, pentavalent, and
pneumococcal vaccines are administered when the child is 6, 10, and 14 weeks old, respec-
tively. These vaccines were administered on the same occasion, and we determined that the
data for each vaccine dose were similar. Accordingly, the data are presented as one vaccine
type (pentavalent) over three doses (Figure 4c). Although the coverage of all three doses
in all years in Coastal Hadhramaut was >85%, the coverage of doses 1 and 2 decreased in
2016. Subsequently, their coverage increased together with that of the other vaccines until
2020, when all doses decreased by approximately 9% compared to 2019.
The district-level analysis demonstrated that all districts exhibited increased coverage
of pentavalent vaccine doses 1 and 2 from 2013 to 2019. Furthermore, all districts had
high coverage except Hajer in 2013–2017, Broome-Mayfa’a in 2013 and 2014, Al-Shahr
in 2016, Ghail Bawazeer in 2015 and 2016, Yeabeth in 2017, and Al-Dees in 2013 and
2014, which had <80% coverage. In 2020, all districts demonstrated decreased coverage
compared to previous years. Generally, increased coverage was recorded for pentavalent
vaccine dose 3 over the years in all districts, except for Al-Dees in 2014, Hajer in 2014 and
2015, and Yeabeth in 2017, which demonstrated decreased coverage. In 2020, all districts
demonstrated decreased coverage compared to 2019, where Al-Shahr and Al-Dees had
<80% coverage while all other districts had a high coverage rate (Tables S7–S9).
4. Discussion
Our results and evidence in the literature indicate a possible connection between the
effect of war and the COVID-19 pandemic on the achievement of immunization status.

Vaccines 2024,12, 311 9 of 13
Vaccination coverage is a significant indicator for tracking and guiding immunization
programs at all levels. In the present study, we described the vaccination coverage trend
in children living in Coastal Hadhramaut, Yemen, in 2013–2020 (before and after the civil
war and 1 year during the COVID-19 pandemic). Our results revealed decreased coverage
for most vaccines in Coastal Hadhramaut in 2015 and 2016. In 2020, vaccination coverage
was decreased for all vaccine types. The reasons for the decrease are multifactorial and
were exacerbated by the ongoing conflict and pandemic. Nevertheless, the results can be
attributed to several factors, such as parents, healthcare system accessibility, vaccine stock
availability, and the public health emergencies that disrupted health program management
and monitoring.
4.1. Public Health Emergency and Vaccination Coverage in Yemen
4.1.1. Conflict and Humanitarian Crisis
The Yemen civil war began in 2015–2016. While the Hadhramaut Governorate was
not directly involved in the war, the political, economic, and social war affected all Yemeni
regions [
4
]. Furthermore, the local Al-Qaida branch seized Al-Mukalla, the Hadhramaut
Governorate capital, and the surrounding regions in 2015, and controlled them for ap-
proximately 1 year. Consequently, the situation isolated Coastal Hadhramaut from direct
governmental control [22].
During a conflict, human requirements are restricted to basic life needs. Together with
the unstable local conditions, immunization was considered an additional requirement
that could be delayed or even abandoned. Furthermore, the thousands of people who had
escaped war and migrated to Hadhramaut increased general local society demands and
complicated the living situation. Moreover, the difficulty in tracking and reaching displaced
populations contributed to the decreased vaccine coverage. Yemeni healthcare infrastruc-
ture was weak even before the conflict, where access to healthcare facilities was limited,
especially in rural areas. The conflict exacerbated the situation and led to the destruction or
closure of many health centers and clinics [
18
]. Although several immunization campaigns
were held in 2014–2020, the lack of functioning healthcare facilities and trained personnel
prevented the provision of many health services, including immunization [
17
]. Addition-
ally, a lack of awareness of immunization importance, incorrect ideas, misinformation,
and rumors regarding vaccination, especially in communities with internal conflict, affect
parents’ decisions about vaccinating their children, as parents are concerned about vaccine
safety and efficacy specifically during the conflict, leading to a reluctance to vaccinate their
children [14,28].
Our results agreed with the results of other studies conducted in Yemen, where most
concluded that vaccination coverage decreased markedly after the war began [
4
,
14
,
29
,
30
].
Torbosh et al. conducted a study using EPI administrative data for all governorates
in 2012–2015 (before and 1 year after the civil war) to determine the effect of the 2015
war on the immunization coverage of children under 1 year old in Yemen. The analysis
of the 2012–2015 vaccination coverage data revealed that the war negatively affected
immunization coverage. The analysis determined that the pentavalent-3 vaccine coverage
was 82% in 2012 and 88% in 2014, the measles vaccine coverage was 70% in 2012 and
75% in 2014, while the 2015 coverage for the pentavalent-3 and measles vaccines was
84% and 66%, respectively. That study concluded that there were greater reductions in
governorates with armed confrontations, while governorates that did not have armed
confrontations had increased coverage [
14
]. Other studies reported that immunization
coverage significantly affected vaccination services, which mainly explained the current
increase in cases of VPDs, such as measles, diphtheria, and diarrheal diseases throughout
the country, which led to outbreaks [
4
,
16
,
31
]. In 2017, a diphtheria outbreak was confirmed
in Yemen, where 2203 probable diphtheria cases (including 116 deaths) were reported [
16
].
Furthermore, measles outbreaks were reported in different years in Yemen, with more than
3000 suspected cases being reported throughout the country in 2018 [
32
]. UNICEF launched
a nationwide vaccination campaign against childhood diseases, targeting 5.4 million Yemeni

Vaccines 2024,12, 311 10 of 13
children. However, the vaccination coverage reported remained unsatisfactory, although
the Hadhramaut Governorate was one of the governorates with better and more stable
social conditions at that time [33].
4.1.2. COVID-19 Pandemic
Following the detection of the first Yemeni case of COVID-19 in Hadhramaut in April
2020, the imposed curfew, fear of infection, and general vaccine hesitancy all reduced
public interest in any other health care than protecting themselves against COVID-19
infection. These conditions persisted in 2020 and 2021 until the COVID-19 vaccine became
available in the country, which brought hope and relief. The literature also supported the
reports of decreased immunization coverage during the COVID-19 pandemic, where the
pandemic affected routine immunization globally and a greater effect was expected in
LMICs [
23
,
34
–
37
]. A recent study conducted in Ecuador (an LMIC) that aimed to assess
the vaccination coverage during the pandemic in 2020 reported a decreased number of
vaccine doses and vaccination coverage for infants for the rotavirus, poliovirus, PCV, and
pentavalent vaccines as compared to previous years [
20
]. The study also explained that the
causes of decreased vaccination coverage could be related to parental choices to use another
method for immunity, misconception, national lockdowns, mobilization restrictions, and
fear of infection [
20
]. Similarly, a study conducted in Pakistan to investigate the effect
of the COVID-19 lockdown on routine immunization reported the same conclusion [
23
].
Based on WHO, UNICEF, Global Alliance for Vaccine Initiative (GAVI), and Sabin Vaccine
Institute data, COVID-19 hindering vaccination services in at least 68 countries placed
approximately 80 million children under the age of 1 year at risk of childhood VPDs
such as diphtheria, pertussis, polio, hepatitis B, pneumococcus, measles, and rotavirus
infections [
19
]. Furthermore, lockdowns, social distancing, the fear of contagion, and supply
chain interruption compelled parents to delay their children’s routine immunization [
23
,
38
].
Our results indicated that immunization coverage increased in 2016–2019, which was
attributed to the improved social situation in Hadhramaut, as Houthi rebels were expelled
from most of the southern governorates, and Al-Qaida was ousted in 2016 [
22
]. Thus,
life returned to an acceptable state although the war continued. The people had become
accustomed to the current conditions, and a large proportion of displaced people had
returned to their original regions. These changes provided residents with the opportunity
to consider their children’s health and seek immunization centers to resume or start their
children’s immunization programs. The healthcare authorities cooperated with the WHO
and UNICEF to conduct several vaccination campaigns, especially in 2018–2019 [39].
4.2. The Effect of Civil War and the COVID-19 Pandemic on SDG 3 Achievement
Both the civil war and the COVID-19 pandemic greatly affected the achievement of
SDG 3 in Yemen (and hence Hadhramaut). The Yemeni healthcare system collapsed during
the ongoing conflict, and many healthcare centers were destroyed or became non-functional.
The damaged infrastructure, road closures, and ongoing violence restricted access to health-
care services, which limited the availability of essential healthcare services and affected
progress toward SDG 3 [
18
]. The exacerbated humanitarian crisis led to widespread food
insecurity, malnutrition, and displacement, which weakened the immune systems of many
Yemenis and rendered them more susceptible to disease. Thus, the weakened healthcare
system, limited access to clean water and sanitation, malnutrition, and overcrowded living
conditions created favorable conditions for disease spread. Consequently, many commu-
nicable disease outbreaks occurred in 2014–2020, such as cholera, measles, dengue fever,
diphtheria, and COVID-19 [
16
,
22
,
30
]. These outbreaks presented additional challenges
to achieving SDG 3 [
4
]. Furthermore, immunization programs in Yemen were disrupted,
which decreased immunization coverage [
14
], affected Yemeni children’s well-being, and
hindered progress toward SDG 3 and the achievement of other interconnected SDGs [3].
Although this study presented a significant overview of childhood vaccination cov-
erage during the main crisis in Yemen in the past decade, it was also subject to some

Vaccines 2024,12, 311 11 of 13
limitations. First, we used data from EPI departments and obtained complete data for only
8 years (2013–2020). The 2 years of data pre-2013 (2011–2012) were incomplete and thus
they were excluded from the analysis. Secondly, as in other LMICs, no census has been
conducted recently in Yemen; the last census was conducted in 2004. The EPI data use the
population projection for the current years based on 2004 census data as no census data
have been available since then. We used the EPI data in the same manner in the present
study and might have overestimated or underestimated the vaccination coverage due to
the estimation of the target population.
5. Conclusions
The humanitarian conflict and COVID-19 pandemic negatively affected childhood
vaccination coverage in Coastal Hadhramaut, Yemen. The trend correlated with the stage
of the humanitarian crisis and previous studies conducted in Yemen. Efforts to address
the challenges require comprehensive approaches (humanitarian assistance, peacebuilding
initiatives, and long-term development strategies) to restore and strengthen the healthcare
system and achieve sustainable progress towards SDG 3. Public health professionals should
address misconceptions and concerns by increasing the awareness of the importance of
vaccinations and providing clear, culturally sensitive information on vaccine benefits and
safety. The continuous and timely assessment of vaccination coverage is required to respond
to the emergency crises in Yemen. Furthermore, countries, especially LMICs such as Yemen,
should establish and maintain a preparedness plan to overcome emergencies. Moreover,
further research to evaluate the consequences of the public health crisis on childhood
vaccination coverage is recommended.
Supplementary Materials:
The following supporting information can be downloaded at: https://
www.mdpi.com/article/10.3390/vaccines12030311/s1, Table S1: BCG vaccine coverage in Coastal
Hadhramout (2013–2020). Table S2: IPV vaccine coverage in Coastal Hadhramout (2013–2020). Table
S3: MR 1 vaccine coverage in Coastal Hadhramout (2013–2020). Table S4: MR 2 vaccine coverage in
Coastal Hadhramout (2013–2020). Table S5: Rota 1 vaccine coverage in Coastal Hadhramout (2013–2020).
Table S6: Rota 2 vaccine coverage in Coastal Hadhramout (2013–2020). Table S7: Pentavalent 1 vaccine
coverage in Coastal Hadhramout (2013–2020). Table S8: Pentavalent 2 vaccine coverage in Coastal
Hadhramout (2013–2020). Table S9: Pentavalent 3 vaccine coverage in Coastal Hadhramout (2013–2020).
Author Contributions:
S.A.B. conducted the study, analyzed the data, and reported the work de-
scribed in the article; R.S. conceptualized the research idea and critically reviewed the article; H.I.
and A.S.B.-G. critically reviewed the final manuscript; R.S. acted as article guarantor. All authors
have read and agreed to the published version of the manuscript.
Funding:
Financial support for the proofreading of the article and payment of the Article Processing
Charge (APC) was granted by the Faculty of Medicine, Universiti Kebangsaan Malaysia (UKM),
Cheras, Kuala Lumpur, Malaysia (grant number TAP K011901). The funder was not involved in any
decision-making in the report.
Institutional Review Board Statement:
The study was conducted in accordance with the Declara-
tion of Helsinki and approved by the Universiti Kebangsaan Malaysia Research Ethics Committee
(protocol code FF-2021-051; date of approval: 18 February 2021).
Informed Consent Statement:
Not applicable as this manuscript was prepared based on sec-
ondary data.
Data Availability Statement: All data relevant to this manuscript are included in the manuscript text.
Acknowledgments:
We thank the UKM Faculty of Medicine, which provided financial support for
the publication of this manuscript (proofreading and APC). We acknowledge the Immunization
Department at the Public Health and Population Office in Coastal Hadhramaut for providing the
assistance and information necessary to conduct this study. A special thanks to Fouad Ali Bamatref,
Director of the Immunization Program at the time of our study, who aided us in obtaining the data.

Vaccines 2024,12, 311 12 of 13
Conflicts of Interest:
The authors declare no conflicts of interest. The funders had no role in the
design of the study; in the collection, analyses, or interpretation of data; in the writing of the
manuscript; or in the decision to publish the results.
References
1.
World Health Organization. World Health Statistics 2021: Monitoring Health for the SDGs, Sustainable Development Goals; World
Health Organization: Geneva, Switzerland, 2021.
2.
World Health Organization. 2018 Assessment Report of the Global Vaccine Action Plan: Strategic Advisory Group of Experts on
Immunization; World Health Organization: Geneva, Switzerland, 2018.
3.
World Health Organization. Immunization Agenda 2030: A Global Strategy to Leave No One Behind; World Health Organization:
Geneva, Switzerland, 2020.
4.
El Bcheraoui, C.; Jumaan, A.O.; Collison, M.L.; Daoud, F.; Mokdad, A.H. Health in Yemen: Losing ground in war time. Glob.
Health 2018,14, 42. [CrossRef]
5.
Sutan, R.; Batarfi, S.A.; Ismail, H.; Bin-Ghouth, A.S. Vaccine hesitancy from parents and healthcare providers perspectives in
Ha-dhramout Governorate, Yemen: A mixed-method study protocol. BMJ Open 2022,12, e055841. [CrossRef] [PubMed]
6.
IPC-IG, UNICEF-Yemen. Yemen National Social Protection Monitoring Survey (NSPMS): 2012–2013—Final Report; International
Policy Centre for Inclusive Growth: Brasilia, Brazil, 2015.
7.
Muhoza, P.; Danovaro-Holliday, M.C.; Diallo, M.S.; Murphy, P.; Sodha, S.V.; Requejo, J.H.; Wallace, A.S. Routine vaccination
coverage—Worldwide, 2020. MMWR Morb. Mortal. Wkly. Rep. 2021,70, 1495–1500. [CrossRef]
8.
World Health Organization. Eastern Mediterranean Vaccine Action Plan 2016–2020: A Framework for Implementation of the Global
Vaccine Action Plan; Regional Office for the Eastern Mediterranean, World Health Organization: Geneva, Switzerland, 2019.
9.
Peck, M.; Gacic-Dobo, M.; Diallo, M.S. Global routine vaccination coverage, 2018/Couverture de la vaccination systematique
dans le monde, 2018. Wkly. Epidemiol. Rec. 2019,94, 498–505.
10.
Haffajee, R.; Parmet, W.E.; Mello, M.M. What Is a Public Health “Emergency”? N. Engl. J. Med.
2014
,371, 986–988. [CrossRef]
[PubMed]
11.
Brown, R.C.; Witt, A.; Fegert, J.M.; Keller, F.; Rassenhofer, M.; Plener, P.L. Psychosocial interventions for children and adolescents
after man-made and natural disasters: A meta-analysis and systematic review. Psychol. Med. 2017,47, 1893–1905. [CrossRef]
12.
Alruwaili, A.; Islam, S.; Usher, K. Disaster preparedness in hospitals in the middle east: An integrative literature review. Disaster
Med. Public Health Prep. 2019,13, 806–816. [CrossRef]
13.
Naser, W.N.; Saleem, H.B. Emergency and disaster management training; knowledge and attitude of Yemeni health professionals-
a cross-sectional study. BMC Emerg. Med. 2018,18, 23. [CrossRef]
14.
Torbosh, A.; Al Amad, M.A.; Al Serouri, A.; Khader, Y. The Impact of War in Yemen on Immunization Coverage of Children
Under One Year of Age: Descriptive Study. JMIR Public Health Surveill. 2019,5, e14461. [CrossRef]
15.
OCHA-Yemen. 2019 Humanitarian Needs Overview: Yemen; United Nations Office for the Coordination of Humanitarian Affairs:
New York, NY, USA, 2018.
16.
Dureab, F.; Al-Sakkaf, M.; Ismail, O.; Kuunibe, N.; Krisam, J.; Müller, O.; Jahn, A. Diphtheria outbreak in Yemen: The impact of
conflict on a fragile health system. Confl. Health 2019,13, 19. [CrossRef]
17.
Tappis, H.; Elaraby, S.; Elnakib, S.; AlShawafi, N.A.A.; BaSaleem, H.; Al-Gawfi, I.A.S.; Othman, F.; Shafique, F.; Al-Kubati, E.;
Rafique, N.; et al. Reproductive, maternal, newborn and child health service delivery during conflict in Yemen: A case study.
Confl. Health 2020,14, 30. [CrossRef]
18.
Qirbi, N.; Ismail, S.A. Health system functionality in a low-income country in the midst of conflict: The case of Yemen. Health
Policy Plan. 2017,32, 911–922. [CrossRef] [PubMed]
19.
Lassi, Z.S.; Naseem, R.; Salam, R.A.; Siddiqui, F.; Das, J.K. The impact of the COVID-19 pandemic on immunization campaigns
and programs: A systematic review. Int. J. Environ. Res. Public Health 2021,18, 988. [CrossRef] [PubMed]
20.
Suárez-Rodríguez, G.L.; Salazar-Loor, J.; Rivas-Condo, J.; Rodríguez-Morales, A.J.; Navarro, J.-C.; Ramírez-Iglesias, J.R. Routine
im-munization programs for children during the COVID-19 pandemic in Ecuador, 2020—Hidden effects, predictable consequences.
Vaccines 2022,10, 857. [CrossRef]
21.
Bin-Ghouth, A.; Alsheikh, G. The COVID-19 Pandemic and Health Inequalities in Yemen. J. Community Med. Health Care
2020
,5, 1042.
22. Odey, J. Great Disaster: The Impact of COVID-19 on Yemen. Lib. Univ. J. Statesmanship Public Policy 2022,2, 7.
23.
Chandir, S.; Siddiqi, D.A.; Mehmood, M.; Setayesh, H.; Siddique, M.; Mirza, A.; Soundardjee, R.; Dharma, V.K.; Shah, M.T.;
Abdullah, S.; et al. Impact of COVID-19 pandemic response on uptake of routine immunizations in Sindh, Pakistan: An analysis
of provincial electronic immunization registry data. Vaccine 2020,38, 7146–7155. [CrossRef]
24.
Free Map Viewer. Map—Yemen. Available online: https://www.freemapviewer.org/en/map/Map-Yemen_189.html#google_
vignette (accessed on 10 March 2024).
25.
Health Affairs Office Hadhramout Governorate. The Statistical Report for the Year 2021 of the Health Office in Hadhramaut Governorate;
Republic of Yemen Ministry of Health & Population, Health Affairs Office Hadhramout Governorat: Sana’a, Yemen, 2021.
26.
Ministry of Public Health and Population Yemen. A Practical Guide for Health Workers Vaccination Services Providers; Ministry of
Public Health and Population Yemen: Sana’a, Yemen, 2009.

Vaccines 2024,12, 311 13 of 13
27.
World Health Organization. World Health Organization Vaccination Coverage Cluster Surveys: Reference Manual; World Health
Organization: Geneva, Switzerland, 2018.
28.
Domek, G.J.; O’Leary, S.T.; Bull, S.; Bronsert, M.; Contreras-Roldan, I.L.; Ventura, G.A.B.; Kempe, A.; Asturias, E.J. Measuring
vaccine hesitancy: Field testing the WHO SAGE Working Group on Vaccine Hesitancy survey tool in Guatemala. Vaccine
2018
,36,
5273–5281. [CrossRef]
29. Burki, T. Yemen’s neglected health and humanitarian crisis. Lancet 2016,387, 734–735. [CrossRef]
30.
Qirbi, N.; Ismail, S.A. Ongoing threat of a large-scale measles outbreak in Yemen. Lancet Glob. Health
2016
,4, e451. [CrossRef]
[PubMed]
31.
Raslan, R.; El Sayegh, S.; Chams, S.; Chams, N.; Leone, A.; Hussein, I.H. Re-emerging vaccine-preventable diseases in war-affected
peoples of the eastern mediterranean region—An update. Front. Public Health 2017,5, 283. [CrossRef]
32.
Raad, I.I.; Chaftari, A.-M.; Dib, R.W.; Graviss, E.A.; Hachem, R. Emerging outbreaks associated with conflict and failing healthcare
systems in the Middle East. Infect. Control. Hosp. Epidemiol. 2018,39, 1230–1236. [CrossRef]
33. Yuan, X. Concern over reported number of measles cases in Yemen. Lancet 2018,391, 1886. [CrossRef]
34.
Hossain, M.; Abdulla, F.; Karimuzzaman, M.; Rahman, A. Routine Vaccination Disruption in Low-Income Countries: An Impact
of COVID-19 Pandemic. Asia Pac. J. Public Health 2020,32, 509–510. [CrossRef]
35.
Baghdadi, L.R.; Younis, A.; Al Suwaidan, H.I.; Hassounah, M.M.; Al Khalifah, R. Impact of the COVID-19 pandemic lockdown on
routine childhood immunization: A saudi nationwide cross-sectional study. Front. Pediatr. 2021,9, 692877. [CrossRef]
36.
Alves, J.G.; Figueiroa, J.N.; Urquia, M.L. Impact of COVID-19 on immunization of Brazilian infants. Int. J. Infect. Dis.
2021
,107,
252–253. [CrossRef] [PubMed]
37.
Domingues, C.M.A.S.; da Silva Teixeira, A.M.; de Moraes, J.C. Vaccination coverage in children in the period before and during
the COVID-19 pandemic in Brazil: A time series analysis and literature review. J. Pediatr.
2022
,99, S12–S21. [CrossRef] [PubMed]
38.
Ota, M.O.C.; Badur, S.; Romano-Mazzotti, L.; Friedland, L.R. Impact of COVID-19 pandemic on routine immunization. Ann. Med.
2021,53, 2286–2297. [CrossRef] [PubMed]
39.
World Health Organization. Yemen: Update on the Expanded Programme on Immunization 2019. Available online: https://www.
emro.who.int/yem/yemeninfocus/update-on-the-expanded-programme-on-immunization- september-2019.html (accessed on
28 November 2023).
Disclaimer/Publisher’s Note:
The statements, opinions and data contained in all publications are solely those of the individual
author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to
people or property resulting from any ideas, methods, instructions or products referred to in the content.