Laith J Abu-Raddad

• PhD
• Professor at Weill Cornell Medicine-Qatar

Background This study investigated the presence of the healthy vaccinee effect—the imbalance in health status between vaccinated and unvaccinated individuals—in two rigorously conducted COVID-19 vaccine effectiveness studies involving primary series and booster vaccinations. It also examined the temporal patterns and variability of this effect acro...

Hepatitis C virus (HCV) infection poses a global health challenge, yet its epidemiology in Qatar remains underexplored. This study estimated HCV antibody (Ab) prevalence in Qatar and examined associated socio-demographic factors. From January 2017 to December 2019, the Ministry of Public Health conducted a national HCV awareness and surveillance ca...

Accurate Vitamin B12 (Vit B12) quantification is essential for diagnosing deficiencies linked to neurological and hematological disorders. The Accre 8 Point-of-Care (POC) Chemiluminescent Immunoassay (CLIA) system offers a compact design, rapid single-step operation, and minimal calibration requirements. This study evaluates Accre 8’s performance a...

Background SARS-CoV-2 infection is associated with protection against reinfection. This study analysed this protection across different reinfection symptoms and severities, comparing the preomicron and omicron eras. Methods A nationwide, matched, test-negative, case–control study was conducted in Qatar from 5 February 2020 to 12 March 2024. The pr...

Background Herpes simplex virus type 1 (HSV-1) is a highly infectious, globally prevalent lifelong infection. Despite advancements in understanding its epidemiology, the assortativeness in the age-dependent transmission patterns remains unclear. This study aimed to estimate the degree of assortativeness in age group mixing for oral-to-oral HSV-1 tr...

Background Syphilis remains a significant global public health concern, contributing substantially to morbidity and mortality. Given syphilis’ asymptomatic nature, varied clinical presentations, and severe untreated complications, accurate diagnostic methods are crucial. Aim This study aims to evaluate the performance of the new treponemal test, M...

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...

Background SARS-CoV-2 infection protection against reinfection can be compromised by emergence of immune-evasive variants. Methods A national, matched, test-negative, case-control study was conducted on Qatar's population between February 5, 2020-February 12, 2024, to assess the level and durability of protection offered by omicron infection again...

Background There are contradictory reports regarding the association of COVID-19 with sudden cardiac deaths. It is unclear whether these deaths are the result of known cardiac disease and risk factors or are unexpected based on prevalent risk factors. Our aim was to determine the association between COVID-19 infection and UCD among individuals who...

Objectives Genital herpes simplex virus (HSV) type 1 and 2 infections are lifelong and can cause symptomatic genital ulcer disease (GUD). HSV-2 almost always causes sexually transmitted genital infection, while HSV-1 mainly causes oral infection but can be sexually transmitted to cause genital infection. This study estimated genital infection with...

We aimed to understand to what extent knowledge of the prevalence of one sexually transmitted infection (STI) can predict the prevalence of another STI, with application for men who have sex with men (MSM). An individual-based simulation model was used to study the concurrent transmission of HIV, HSV-2, chlamydia, gonorrhea, and syphilis in MSM sex...

Objectives The chemiluminescence immunoassay automated Abbott ARCHITECT hepatitis B surface antigen (HBsAg) screening assay is globally recognized for its superior sensitivity but notably low specificity. This mandates positive results confirmation by another confirmatory assay, such as the widely used Abbott ARCHITECT HBsAg neutralizing assay. Thi...

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 Social distancing restrictions during the COVID-19 pandemic caused disruptions to sexual health services (SHS) worldwide. During the first year of the pandemic, Lebanon implemented multiple lockdowns during which SHS endured repetitive closures. We explore the impact of the pandemic on SHS delivery and the diagnosis rate of sexually tran...

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 The epidemiology of Neisseria gonorrhoeae (NG) infection in the Middle East and North Africa (MENA) region remains poorly understood, despite the global recognition of its disease burden and the growing concern regarding antimicrobial resistance. This study aimed to systematically review the evidence on NG prevalence in MENA, estimate th...

Introduction To estimate the impact of reducing obesity, smoking, and physical inactivity (PIA) prevalence, and of introducing physical activity (PA) as an explicit intervention, on the prevalence, incidence, and mortality of type 2 diabetes mellitus (T2DM) in Oman. Research design and methods A deterministic population-level mathematical model wa...

This study aimed to analytically describe the epidemiology of herpes simplex virus type 1 (HSV-1) infection in the United States through a systematic review and meta-analytics. We reviewed 159 publications, identifying 190 seroprevalence measures and 43 proportions of HSV-1 detection in genital herpes. The pooled mean HSV-1 seroprevalence was 38.0%...

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...

The CLIA automated Abbott-Architect HBsAg screening assay is globally recognized for its superior sensitivity but notably low specificity. This mandates positive results confirmation by another confirmatory assay, such as the widely used Abbott-Architect HBsAg neutralizing assay. Aim: To evaluate performance of the new CLIA Mindray-CL-900i HBsAg sc...

Background Trichomoniasis, caused by the parasite Trichomonas vaginalis (TV), remains an underappreciated sexually transmitted infection (STI), primarily due to inadequate understanding of its epidemiology and public health implications. This study aimed to characterize TV epidemiology in the Middle East and North Africa (MENA). Methods Systematic...

Background Hepatitis A virus (HAV) is the predominant cause of acute viral hepatitis worldwide; however, data on HAV antibody prevalence (seroprevalence) among migrant populations are limited. This study aimed to investigate HAV seroprevalence among Qatar’s migrant craft and manual workers (CMWs), constituting approximately 60% of the country’s pop...

Objectives Hepatitis C virus (HCV) infection poses a global health challenge. By the end of 2021, the WHO estimated that less than a quarter of global HCV infections had been diagnosed. There is a need for a public health tool that can facilitate the identification of people with HCV infection and link them to testing and treatment, and that can be...

Sexually transmitted infections (STIs) are widespread worldwide and negatively affect sexual and reproductive health. Gaps in evidence and in available tools have long hindered STI programmes and policies, particularly in resource-limited settings. In 2022, WHO initiated a research prioritisation process to identify the most important STI research...

Background Syphilis is a sexually transmitted infection (STI) that can be prevented and effectively treated; yet it continues to be a cause of morbidity and mortality worldwide. There is a limited understanding of the epidemiology of syphilis in the Middle East and North Africa (MENA) region. Methods A systematic review conducted up to April 30, 2...

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: Genital herpes simplex virus (HSV) type 1 and 2 infections are lifelong and can cause symptomatic genital ulcer disease (GUD). HSV-2 almost always causes sexually transmitted genital infection, while HSV-1 mainly causes oral infection but can be sexually transmitted to cause genital infection. This study estimated genital infection with...

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...

Background Priming with ChAdOx1 followed by heterologous boosting is considered in several countries. Nevertheless, analyses comparing the immunogenicity of heterologous booster to homologous primary vaccination regimens and natural infection are lacking. In this study, we aimed to conduct a comparative assessment of the immunogenicity between homo...

This study evaluated the potential for antibody‐dependent enhancement (ADE) in serum samples from patients exposed to Middle East respiratory syndrome coronavirus (MERS‐CoV). Furthermore, we evaluated the effect of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) vaccination on ADE in individuals with a MERS infection history. We perfor...

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.

The prevalence of Chlamydia trachomatis, Neisseria gonorrhoeae, and Trichomonas vaginalis was determined among 431 pregnant Syrian refugee women seeking antenatal care in Lebanon. Low prevalence at 0.5% for chlamydia, 0.2% for trichomoniasis, and 0.0% for gonorrhoea was detected, suggesting a low burden of sexually transmitted infection in this pop...

Introduction We aimed to investigate the overlapping epidemiologies of human immunodeficiency virus (HIV), herpes simplex virus type 2 (HSV-2), chlamydia, gonorrhea, and syphilis in sexual networks of men who have sex with men (MSM), and to explore to what extent the epidemiology of one sexually transmitted infection (STI) relates to or differs fro...

Wastewater-based epidemiology (WBE) has been proven effective for the monitoring of infectious disease outbreaks during mass gathering events and for timely public health interventions. As part of Qatar's efforts to monitor and combat the spread of infectious diseases during the FIFA World Cup Qatar 2022™ (FWC’22), wastewater surveillance was used...

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...

Neutralizing antibodies (NAbs) are elicited after infection and vaccination and have been well studied. However, their antibody‐dependent cellular cytotoxicity (ADCC) functionality is still poorly characterized. Here, we investigated ADCC activity in convalescent sera from infected patients with wild‐type (WT) severe acute respiratory syndrome coro...

Background Hepatitis A virus (HAV) is the predominant cause of acute viral hepatitis worldwide; however, data on HAV antibody prevalence (seroprevalence) among migrant populations are limited. This study aimed to investigate HAV seroprevalence among Qatar's migrant craft and manual workers (CMWs), constituting approximately 60% of the country's pop...

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...

Background Epidemiology of Neisseria gonorrhoeae (NG) infection remains inadequately understood. Aim We aimed to characterise NG epidemiology in Europe. Methods We used Cochrane and PRISMA guidelines to systematically review, report, synthesise and analyse NG prevalence data from 1949 to 30 September 2021. Random-effects meta-analyses estimated p...

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...

Background Hepatitis C virus (HCV) infection levels in Jordan remain uncertain. No HCV national population-based survey has ever been conducted in the country. To meet the World Health Organization’s target of reducing HCV incidence to ≤5 per 100,000 people per year by 2030, it is essential to determine the infection levels, identify affected indiv...

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 $...

Neisseria gonorrhoeae infection (gonorrhoea) is a global public health challenge, causing substantial sexual and reproductive health consequences, such as infertility, pregnancy complications and increased acquisition or transmission of HIV. There is an urgency to controlling gonorrhoea because of increasing antimicrobial resistance to ceftriaxone,...

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,...

Tick-borne infections are the most common vector-borne diseases in the USA. Ticks harbor and spread several infections with Lyme disease being the most common tickborne infection in the US and Europe. Lack of awareness about tick populations, specific diagnostic tests, and overlapping symptoms of tick-borne infections can often lead to misdiagnosis...

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 The objective of this study was to characterize herpes simplex virus type 1 (HSV-1) epidemiology in Canada. Methods HSV-1 publications as recent as December 6, 2021 were systematically reviewed, synthesized, and reported following PRISMA guidelines. Meta-analyses and meta-regressions were conducted. Results HSV-1 measures were extracte...

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...

Hepatitis C virus (HCV) infection is a global health challenge. By the end of 2021, WHO estimated that less than quarter of global HCV infections were diagnosed. There is a need for a public health tool that can facilitate identification of infected persons and linking them to testing and treatment. We derived and validated a risk score to identify...

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...

The detrimental impact of foodborne pathogens on human health makes food safety a major concern at all levels of production. Conventional methods to detect foodborne pathogens, such as live culture, high-performance liquid chromatography, and molecular techniques, are relatively tedious, time-consuming, laborious, and expensive, which hinders their...

Aims To predict the epidemiological impact of specific, and primarily structural public health interventions that address lifestyle, dietary, and commuting behaviors of Qataris as well as subsidies and legislation to reduce type 2 diabetes mellitus (T2DM) burden among Qataris. Methods A deterministic population-based mathematical model was used to...

The COVID-19 outbreak of 2020 has required many governments to develop and adopt mathematical-statistical models of the pandemic for policy and planning purposes. To this end, this work provides a tutorial on building a compartmental model using Susceptible, Exposed, Infected, Recovered, Deaths and Vaccinated (SEIRDV) status through time. The propo...

Importance: In the ongoing COVID-19 pandemic, there remain unanswered questions regarding the nature and importance of the humoral immune response against other coronaviruses. Although coinfection of the Middle East respiratory syndrome coronavirus (MERS-CoV) with the SARS-CoV-2 has not been documented yet, several patients previously infected wit...

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...

No MERS-CoV cases were detected during the 2022 FIFA World Cup in Qatar in November–December 2022 which attracted 1.4 million visitors. Robust monitoring mechanisms instituted by Qatar before and during the FIFA WC can serve as a template for future similar events to detect infectious diseases of global importance.

Objective: To investigate all-cause mortality, COVID-19 mortality and all-cause non-COVID-19 mortality in Qatar during the COVID-19 pandemic. Methods: A national, retrospective cohort analysis and national, matched, retrospective cohort studies were conducted between 5 February 2020 and 19 September 2022. Results: There were 5025 deaths during...

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: Priming with ChAdOx1 followed by heterologous boosting have been considered in several countries. Nevertheless, analyses that provide a comparison of the immunogenicity of heterologous booster in comparison to homologous primary vaccination regimens and natural infection are lacking. In this study, we aimed to conduct a comparative asse...

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: Herpes simplex virus type 2 (HSV-2) infection is a prevalent, sexually transmitted infection with poorly characterized prevalence in the Middle East and North Africa (MENA) region. This study characterized HSV-2 epidemiology in MENA. Methods: The systematic review was guided by the Cochrane Collaboration Handbook and findings were re...