Houssein Ayoub

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Verified

Houssein verified their affiliation via an institutional email.

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• PhD in Applied Mathematics and Scientific Computing
• Professor (Associate) at Qatar University

Background Accurately assessing SARS-CoV-2 infection severity is essential for understanding the health impact of the infection and evaluating the effectiveness of interventions. This study investigated whether SARS-CoV-2-associated hospitalizations can reliably measure true COVID-19 severity. Methods The diagnostic accuracy of SARS-CoV-2-associat...

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rapidly evolved over short timescales, leading to the emergence of more transmissible variants such as Alpha and Delta1, 2–3. The arrival of the Omicron variant marked a major shift, introducing numerous extra mutations in the spike gene compared with earlier variants1,2. These ev...

Background The Middle East and North Africa (MENA) region is the most affected by hepatitis C virus (HCV) infection globally. This study aimed to estimate HCV incidence among people who inject drugs (PWID) in MENA and evaluate the impact of interventions. Methods A mathematical model was extended and applied to 13 countries with at least one data...

Objectives Scant data are available on syphilis infection within migrant populations worldwide and in the population of the Middle East and North Africa region. This study investigated the prevalence of both lifetime and recent syphilis infections among migrant craft and manual workers (MCMWs) in Qatar, a diverse demographic representing 60% of the...

Architect-HIV Ag/Ab combo chemiluminescence assay is globally recognized for its sensitivity but has a notable false-positive rate. In this study, we aim to evaluate the performance of a new cost-effective screening alternative, the chemiluminescence Ag/Ab combo assay (CL-900i-HIV) from Mindray, China. We selected 195 archived samples categorized a...

Background This study provides a head‐to‐head comparison of the protection provided by the BNT162b2 and mRNA‐1273 vaccines against SARS‐CoV‐2 infection and against severe COVID‐19, covering primary series and third dose/booster vaccinations over up to 3 years of follow‐up, both before and after the emergence of the omicron variant. Methods Two nat...

Background: This study investigated the presence of the healthy vaccinee bias in two COVID-19 vaccine effectiveness studies, involving primary series and booster vaccinations, as well as its temporal patterns and variability across different subpopulations, by examining the association between COVID-19 vaccination and non-COVID-19 mortality in Qata...

Background There is a need for statistical methodologies that scrutinize civilian casualties in conflicts, evaluating the degree to which the conduct of war affects civilians and breaches the laws of war. Employing an epidemiological method, this study introduced, developed, and applied a novel approach for investigating mortality of civilians vers...

Background: Architect-HIV Ag/Ab combo chemiluminescence assay is globally recognized for its sensitivity but has a notable false-positive rate. Aim:To evaluate the performance of a new cost-effective screening alternative, the chemiluminescence Ag/Ab combo assay (CL-900i-HIV) from Mindray, China. Method: We selected 195 archived samples, classifi...

Limited data exist on viral hepatitis among migrant populations. This study investigated the prevalence of current hepatitis B virus (HBV) infection and lifetime hepatitis C virus (HCV) infection among Qatar's migrant craft and manual workers (CMWs), constituting 60% of the country's population. Sera collected during a nationwide COVID-19 populatio...

Highlight Overall effectiveness of infection in preventing reinfection with SARS-CoV-2 JN.1 variant was estimated at 1.8% (95% CI: -9.3-12.6%), and demonstrated rapid decline over time since the previous infection, decreasing from 82.4% (95% CI: 40.9 to 94.7%) within 3 to less than 6 months, to a negligible level after one year.

Introduction Reinfections are increasingly becoming a feature in the epidemiology of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. However, accurately defining reinfection poses methodological challenges. Conventionally, reinfection is defined as a positive test occurring at least 90 days after a previous infection diagnos...

This study investigated the effectiveness of natural infection in preventing reinfection with the JN.1 variant during a large JN.1 wave in Qatar, using a test-negative case-control study design. The overall effectiveness of previous infection in preventing reinfection with JN.1 was estimated at only 1.8% (95% CI: −9.3-12.6%). This effectiveness dem...

Introduction Chlamydia trachomatis (CT) infection is a global health challenge. New approaches are needed to control CT disease burden. Methods An age-structured deterministic mathematical model calibrated to nationally representative population-based data was developed to investigate the impact of CT vaccination on the population of the USA if a...

The COVID-19 pandemic has highlighted the need to use infection testing databases to rapidly estimate effectiveness of prior infection in preventing reinfection ($P{E}_S$) by novel SARS-CoV-2 variants. Mathematical modeling was used to demonstrate a theoretical foundation for applicability of the test-negative, case-control study design to derive $...

Background Epidemiological evidence for immune imprinting was investigated in immune histories related to vaccination in Qatar from onset of the omicron wave, on December 19, 2021, through September 15, 2022. Methods Matched, retrospective, cohort studies were conducted to investigate differences in incidence of SARS-CoV-2 reinfection in the natio...

Background Risk of short- and long-term all-cause mortality after a primary SARS-CoV-2 infection is inadequately understood. Methods A national, matched, retrospective cohort study was conducted in Qatar to assess the risk of all-cause mortality in the national cohort of people infected with SARS-CoV-2 compared with a reference national control co...

Background We investigated the contribution of age, coexisting medical conditions, sex, and vaccination to incidence of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection and of severe, critical, or fatal COVID‐19 in older adults since pandemic onset. Methods A national retrospective cohort study was conducted in the population...

Objective To assess the evolution of COVID-19 severity and fatality in a unique setting that consistently applied, throughout the pandemic, rigorous and standardised criteria for defining severe COVID-19 outcomes. Methods and analysis We conducted a national cohort study on 312 109 Qatari citizens to investigate incidence of severe, critical or fa...

Laboratory evidence suggests a possibility of immune imprinting for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We investigated the differences in the incidence of SARS-CoV-2 reinfection in a cohort of persons who had a primary Omicron infection, but different vaccination histories using matched, national, retrospective,...

Background The rapid growth of Qatar in the last two decades has attracted a large influx of immigrant craft and manual workers (CMWs) seeking employment in jobs associated with food handling, domestic service, and construction. Nearly 60 % of Qatar's population are expatriates CMWs, including many from hyperendemic countries for HEV. Thus, estimat...

Background Limited data exists on herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) infections in migrant populations. This study investigated HSV-1 and HSV-2 seroprevalences and associations among craft and manual workers (CMWs) in Qatar who constitute 60% of Qatar’s population. Methods A national population-based cross-sectional seroprevale...

Effectiveness of the 50-μg mRNA-1273.214 bivalent vaccine against SARS-CoV-2 infection was modest at 25% in a matched, retrospective, cohort study in Qatar comparing infection incidence in the bivalent cohort to that in the national no-recent-vaccination resident cohort. XBB* immune evasion, immune imprinting effects, or both, may explain findings.

Background: Waning of natural infection protection and vaccine protection highlight the need to evaluate changes in population immunity over time. Population immunity of previous SARS-CoV-2 infection or of COVID-19 vaccination are defined, respectively, as the overall protection against reinfection or against breakthrough infection at a given poin...

Background: Protection against SARS-CoV-2 symptomatic infection and severe COVID-19 of previous infection, mRNA two-dose vaccination, mRNA three-dose vaccination, and hybrid immunity of previous infection and vaccination were investigated in Qatar for the Alpha, Beta, and Delta variants. Methods: Six national, matched, test-negative, case-contro...

Background Direct-acting antivirals opened an opportunity for eliminating hepatitis C virus (HCV) infection in the Middle East and North Africa (MENA), the region most affected by HCV infection. Impact of HCV treatment as prevention (HCV-TasP) was investigated in 19 MENA countries. Methods An age-structured mathematical model was used to assess pr...

Our understanding of SARS-CoV-2 reinfection patterns remains limited. We conducted a longitudinal study using Qatar national SARS-CoV-2 data from February 28, 2020 to June 11, 2023 to investigate incidence of reinfections both prior to and after omicron emergence. The latter analysis excluded individuals with pre-omicron infections. Before omicron...

Background: This study assessed the evolution of COVID-19 severity and fatality by utilizing rigorous and standardized criteria that were consistently applied throughout the pandemic in Qatar. Methods: A national cohort study was conducted on Qataris, using data on COVID-19 acute-care and ICU hospitalizations, as well as severe, critical, and fatal...

Background: Waning of natural infection protection and vaccine protection highlight the need to evaluate changes in population immunity over time. Population immunity of previous SARS-CoV-2 infection or of COVID-19 vaccination are defined, respectively, as the overall protection against reinfection or against breakthrough infection at a given point...

Background: Protection against SARS-CoV-2 symptomatic infection and severe COVID-19 of previous infection, mRNA two-dose vaccination, mRNA three-dose vaccination, and hybrid immunity of previous infection and vaccination were investigated in Qatar for the Alpha, Beta, and Delta variants. Methods: Six national, matched, test-negative, case-control s...

Qatar introduced COVID-19 bivalent vaccination for persons ≥12 years old using the 50-μg mRNA-1273.214 vaccine combining SARS-CoV-2 ancestral and omicron BA.1 strains. We estimated effectiveness of this bivalent vaccine against SARS-CoV-2 infection using a matched, retrospective, cohort study. Matched cohorts included 10,886 persons in the bivalent...

Background: Long-term effectiveness of COVID-19 mRNA boosters in populations with different previous infection histories and clinical vulnerability profiles is inadequately understood. We aimed to investigate the effectiveness of a booster (third dose) vaccination against SARS-CoV-2 infection and against severe, critical, or fatal COVID-19, relati...

Background Risk of short- and long-term all-cause mortality after a primary SARS-CoV-2 infection is inadequately understood. Methods A national, matched, retrospective cohort study was conducted in Qatar to assess the risk of all-cause mortality in the national cohort of people infected with SARS-CoV-2 compared with a reference national control co...

Background Economic losses due to herpes simplex infections in low- and middle-income countries (LMICs) are unknown. We estimated economic and quality-of-life losses due to genital herpes in 2019, in 90 LMICs, and from 2020 to 2030 in 45 countries in the World Health Organization (WHO) Africa. We additionally estimated economic losses due to human...

Background Protection offered by five different forms of immunity, combining natural and vaccine immunity, was investigated against symptomatic SARS-CoV-2 infection from Omicron BA.1 or BA.2, and severe, critical, or fatal COVID-19 from BA.1 or BA.2, in Qatar, between December 23, 2021 and February 21, 2022. Methods Six national, matched, test-neg...

Background: Coronavirus Disease 2019 (COVID-19) vaccine antigen dosage may affect protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, but direct evidence to quantify this effect is lacking. Methods: A matched, retrospective, cohort study that emulated a randomized control trial was conducted in Qatar between F...

Background Some studies have reported that influenza vaccination is associated with lower risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and/or coronavirus disease 2019 (COVID-19) morbidity and mortality. This study aims to estimate effectiveness of influenza vaccination, using Abbott’s quadrivalent Influvac Tetra va...

Background Long-term effectiveness of COVID-19 mRNA boosters in populations with different prior infection histories and clinical vulnerability profiles is inadequately understood. Methods A national, matched, retrospective, target trial cohort study was conducted in Qatar to investigate effectiveness of a third mRNA (booster) dose, relative to a...

Background: The BNT162b2 vaccine against coronavirus disease 2019 (Covid-19) has been authorized for use in children 5 to 11 years of age and adolescents 12 to 17 years of age but in different antigen doses. Methods: We assessed the real-world effectiveness of the BNT162b2 vaccine against infection with severe acute respiratory syndrome coronavi...

Background Epidemiological evidence for immune imprinting was investigated in immune histories related to vaccination in Qatar from onset of the omicron wave, on December 19, 2021, through September 15, 2022. Methods Matched, retrospective, cohort studies were conducted to investigate differences in incidence of SARS-CoV-2 reinfection in the natio...

Background Understanding protection conferred by natural SARS-CoV-2 infection versus COVID-19 vaccination is important for informing vaccine mandate decisions. We compared protection conferred by natural infection versus that from the BNT162b2 (Pfizer–BioNTech) and mRNA-1273 (Moderna) vaccines in Qatar. Methods We conducted two matched retrospecti...

The BA.2.75* sublineage of SARS-CoV-2 B.1.1.529 (omicron) variant escapes neutralizing antibodies. We estimated effectiveness of prior infection in preventing reinfection with BA.2.75* using a test-negative, case-control study design. Effectiveness of prior pre-omicron infection against BA.2.75* reinfection, irrespective of symptoms, was 6.0% (95%...

Background: The future of the SARS-CoV-2 pandemic hinges on virus evolution and duration of immune protection of natural infection against reinfection. We investigated duration of protection afforded by natural infection, the effect of viral immune evasion on duration of protection, and protection against severe reinfection, in Qatar, between Febr...

In 2021, Qatar experienced considerable incidence of SARS-CoV-2 infection that was dominated sequentially by the Alpha, Beta, and Delta variants. Using the cycle threshold (Ct) value of an RT-qPCR-positive test to proxy the inverse of infectiousness, we investigated infectiousness of SARS-CoV-2 infections by variant, age, sex, vaccination status, p...

We investigated epidemiological evidence for immune imprinting by comparing incidence of re-reinfection in the national cohort of individuals with a documented Omicron (BA.1/BA.2) reinfection after a pre-Omicron primary infection (designated as the reinfection cohort), to incidence of reinfection in the national cohort of individuals with a documen...

There is significant genetic distance between SARS-CoV-2 Omicron (B.1.1.529) variant BA.1 and BA.2 sub-lineages. This study investigates immune protection of infection with one sub-lineage against reinfection with the other sub-lineage in Qatar during a large BA.1 and BA.2 Omicron wave, from December 19, 2021 to March 21, 2022. Two national matched...

Background The BNT162b2 COVID-19 vaccine is authorized for children 5-11 years of age and adolescents 12-17 years of age, but in different dose sizes. We assessed BNT162b2 real-world effectiveness against SARS-CoV-2 infection among children and adolescents in Qatar. Methods Three matched, retrospective, target-trial, cohort studies were conducted...

This study estimates the effectiveness of previous infection with SARSCoV2 in preventing reinfection with Omicron BA.4/BA.5 subvariants using a test negative, case control study design. Cases (SARSCoV2 positive test results) and controls (SARSCoV2 negative test results) were matched according to sex, 10 year age group, nationality, comorbid conditi...

In 2021, Qatar experienced considerable incidence of SARS-CoV-2 infection that was dominated sequentially by the Alpha, Beta, and Delta variants. Using the cycle threshold (Ct) value of an RT-qPCR-positive test to proxy the inverse of infectiousness, we investigated infectiousness of SARS-CoV-2 infections by variant, age, sex, vaccination status, p...

BACKGROUND The future of the SARS-CoV-2 pandemic hinges on virus evolution and duration of immune protection of natural infection against reinfection. We investigated duration of protection afforded by natural infection, the effect of viral immune evasion on duration of protection, and protection against severe reinfection, in Qatar, between Februa...

Background The incidence of HIV infection among female sex workers and their clients in the Middle East and north Africa is not well known. We aimed to assess HIV incidence, the contribution of heterosexual sex work networks to these numbers, and the effect of interventions by use of mathematical modelling. Methods In this modelling study, we deve...

Background: The protection conferred by natural immunity, vaccination, and both against symptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection with the BA.1 or BA.2 sublineages of the omicron (B.1.1.529) variant is unclear. Methods: We conducted a national, matched, test-negative, case-control study in Qatar from Dece...

SARS-CoV-2 Omicron BA.1 and BA.2 subvariants are genetically divergent. We conducted a matched, test-negative, case-control study to estimate duration of protection of the second and third/booster doses of mRNA COVID-19 vaccines against BA.1 and BA.2 infections in Qatar. BNT162b2 effectiveness was highest at 46.6% (95% CI: 33.4–57.2%) against sympt...

Highlight Compared to BA.1, BA.2 was associated with lower RT-qPCR cycle threshold (Ct) value—3.53 fewer cycles (95% CI: 3.46–3.60), signifying higher infectiousness. This may reflect higher viral load and/or longer duration of infection for BA.2. Natural immunity from previous infection and booster vaccination were associated with less infectious...

Background Prospective observational data show that infected persons with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remain polymerase chain reaction (PCR) positive for a prolonged duration, and that detectable antibodies develop slowly with time. We aimed to analyze how these effects can bias key epidemiological metrics used...

A number of studies reported that influenza vaccination is associated with lower risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and/or coronavirus disease 2019 (COVID-19) morbidity and mortality. We conducted a matched, test-negative, case-control study to estimate effectiveness of influenza vaccination, using Abbott...

Different COVID-19 treatment candidates are under development, and some are becoming available including two promising drugs from Merck and Pfizer. This study provides conceptual frameworks for the effects of three types of treatments, both therapeutic and prophylactic, and to investigate their population-level impact, to inform drug development, l...

BACKGROUND: Protection offered by five different forms of immunity, combining natural and vaccine immunity, was investigated against SARS-CoV-2 Omicron symptomatic BA.1 infection, symptomatic BA.2 infection, BA.1 hospitalization and death, and BA.2 hospitalization and death, in Qatar, between December 23, 2021 and February 21, 2022. METHODS: Six na...

BACKGROUND Protection conferred by natural SARS-CoV-2 infection versus COVID-19 vaccination has not been investigated in rigorously controlled studies. We compared head-to-head protection conferred by natural infection to that from the BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) vaccines in Qatar, between February 28, 2020 and March 6, 2022....

The SARS-CoV-2 Omicron (B.1.1.529) variant has two subvariants, BA.1 and BA.2, that are genetically quite divergent. We conducted a matched, test-negative, case-control study to estimate duration of protection of mRNA COVID-19 vaccines, after the second dose and after a third/booster dose, against BA.1 and BA.2 infections in Qatar population. BNT16...

Background: Waning of vaccine protection against coronavirus disease 2019 (Covid-19) and the emergence of the omicron (or B.1.1.529) variant of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have led to expedited efforts to scale up booster vaccination. Protection conferred by booster doses of the BNT162b2 (Pfizer-BioNTech) and m...

BACKGROUND Qatar experienced a large SARS-CoV-2 Omicron (B.1.1.529) wave that started on December 19, 2021 and peaked in mid-January, 2022. We investigated effects of Omicron subvariant (BA.1 and BA.2), previous vaccination, and prior infection on infectiousness of Omicron infections, between December 23, 2021 and February 20, 2022. METHODS Univar...

BACKGROUND The SARS-CoV-2 Omicron (B.1.1.529) variant has two main sub-lineages, BA.1 and BA.2 with significant genetic distance between them. This study investigated protection of infection with one sub-lineage against reinfection with the other sub-lineage in Qatar during a large BA.1 and BA.2 Omicron wave, from December 19, 2021 to February 21,...

BACKGROUND Qatar has been experiencing a large SARS-CoV-2 Omicron (B.1.1.529) wave that started on December 19, 2021. We assessed duration of protection of BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) COVID-19 vaccines after second dose and after third/booster dose against symptomatic Omicron infection and against COVID-19 hospitalization and...

Background: The effective reproduction number, Rt , is a tool to track and understand pandemic dynamics. This investigation of Rt estimations was conducted to guide the national COVID-19 response in Qatar, from the onset of the pandemic until August 18, 2021. Methods: Real-time "empirical" Rt Empirical was estimated using five methods, including...

One of the main goals of the 2016 Global Health Sector Strategy on viral hepatitis is the elimination of hepatitis C virus (HCV) as a public health problem by 2030, defined as an 80% reduction in incidence and 65% reduction in mortality relative to 2015. Although monitoring HCV incidence is key to validating HCV elimination, use of the gold-standar...

SARS-CoV-2 breakthrough infections in vaccinated individuals and in those who had a prior infection have been observed globally, but the transmission potential of these infections is unknown. The RT-qPCR cycle threshold (Ct) value is inversely correlated with viral load and culturable virus. Here, we investigate differences in RT-qPCR Ct values acr...

BACKGROUND Waning of COVID-19 vaccine protection and emergence of SARS-CoV-2 Omicron (B.1.1.529) variant have expedited efforts to scale up booster vaccination. This study compared protection afforded by booster doses of the BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) vaccines, compared to the primary series of only two doses in Qatar, durin...

BACKGROUND: Natural SARS-CoV-2 infection elicits strong protection against reinfection with the Alpha (B.1.1.7), Beta (B.1.351), and Delta (B.1.617.2) variants. However, the Omicron (B.1.1.529) variant harbors multiple mutations that can mediate immune evasion. We estimated effectiveness of prior infection in preventing reinfection (PES) with Omicr...

Background: The Coronavirus Disease 2019 (COVID-19) pandemic has highlighted an urgent need to use infection testing databases to rapidly estimate effectiveness of prior infection in preventing reinfection (PES) by novel variants of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Methods: Mathematical modeling was used to demonstr...

Background The epidemiology of the SARS-CoV-2 B.1.1.7 (or Alpha) variant is insufficiently understood. This study’s objective was to describe the introduction and expansion of this variant in Qatar and to estimate the efficacy of natural infection against reinfection with this variant. Methods and findings Reinfections with the B.1.1.7 variant and...

BACKGROUND: In early 2021, Qatar launched a mass immunization campaign with Moderna mRNA-1273 COVID-19 vaccine. We assessed persistence of real-world mRNA-1273 effectiveness against SARS-CoV-2 infection and against COVID-19 hospitalization and death. METHODS: Effectiveness was estimated using test-negative, case-control study design, between Januar...

With the global expansion of the highly transmissible SARS-CoV-2 Delta (B.1.617.2) variant, we conducted a matched test-negative case–control study to assess the real-world effectiveness of COVID-19 messenger RNA vaccines against infection with Delta in Qatar’s population. BNT162b2 effectiveness against any, symptomatic or asymptomatic, Delta infec...

Background HHV-6 is the causative agent of exanthema subitum (ES). Transmission mainly occurs through salivary secretions, yet blood transfusions and organ transplantations were also reported as a route of transmission. Studies of HHV-6 seroprevalence in the Middle East and North Africa (MENA) region and other parts of Asia are scarce. Therefore, t...

BACKGROUND Growing evidence suggests that COVID-19 vaccines differ in effectiveness against breakthrough infection or severe COVID-19, but vaccines have yet to be investigated in controlled studies that head-to-head compare immunity of one to another. This study compared protection offered by the mRNA-1273 (Moderna) vaccine with that of the BNT162b...

Importance The effect of prior SARS-CoV-2 infection on vaccine protection remains poorly understood. Objective To assess protection from SARS-CoV-2 breakthrough infection after mRNA vaccination among persons with vs without prior SARS-CoV-2 infection. Design, Setting, and Participants Matched-cohort studies in Qatar for the BNT162b2 (Pfizer-BioNT...

We aimed to estimate, albeit crudely and provisionally, national, regional, and global proportions of respective populations that have been infected with SARS-CoV-2 in the first year after the introduction of this virus into human circulation, and to assess infection morbidity and mortality rates, factoring both documented and undocumented infectio...