Browsing by Author "Al-Kuwari, Einas"
Now showing items 1-20 of 23
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Assessing healthy vaccinee effect in COVID-19 vaccine effectiveness studies: a national cohort study in Qatar.
( National Center for Biotechnology Information , 2025 , Article)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 ... -
Bivalent mRNA-1273.214 vaccine effectiveness against SARS-CoV-2 omicron XBB* infections
(2023 , Article)In October of 2022, Qatar introduced COVID-19 bivalent vaccination for persons ≥ 12 years using the 50-μg mRNA-1273.214 vaccine combining SARS-CoV-2 ancestral and omicron BA.1 strains.1 We estimated this vaccine’s effectiveness ... -
BNT162b2 Versus mRNA-1273 Vaccines: Comparative Analysis of Long-Term Protection Against SARS-CoV-2 Infection and Severe COVID-19 in Qatar
( Wiley , 2024 , Article)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 ... -
Characterizing the Qatar advanced-phase SARS-CoV-2 epidemic
( springer nature , 2021 , Article)The overarching objective of this study was to provide the descriptive epidemiology of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) epidemic in Qatar by addressing specific research questions through a ... -
COVID-19 risk score as a public health tool to guide targeted testing: A demonstration study in Qatar
( Public Library of Science , 2022 , Article)We developed a Coronavirus Disease 2019 (COVID-19) risk score to guide targeted RTPCR testing in Qatar. The Qatar national COVID-19 testing database, encompassing a total of 2,688,232 RT-PCR tests conducted between February ... -
Differential protection against SARS-CoV-2 reinfection pre- and post-Omicron
( Springer Nature , 2025 , Article)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 ... -
Duration of mRNA vaccine protection against SARS-CoV-2 Omicron BA.1 and BA.2 subvariants in Qatar.
( Nature Research , 2022 , Article)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 ... -
Effect of mRNA Vaccine Boosters against SARS-CoV-2 Omicron Infection in Qatar.
( Massachusetts Medical Society , 2022 , Article)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 ... -
Effectiveness and durability of a fourth dose of ancestral-strain mRNA vaccines against SARS-CoV-2 infection: a nationwide matched cohort study in Qatar
( Nature Research , 2025 , Article)Concerns about waning immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the emergence of new variants underscore the need for booster doses. Using a matched cohort design, this ... -
Effects of Previous Infection and Vaccination on Symptomatic Omicron Infections.
( Massachusetts Medical Society , 2022 , Article)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) ... -
Effects of previous infection, vaccination, and hybrid immunity against symptomatic Alpha, Beta, and Delta SARS-CoV-2 infections: an observational study
( Elsevier , 2023 , Article)BackgroundProtection 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 ... -
Effects of SARS-CoV-2 Alpha, Beta, and Delta variants, age, vaccination, and prior infection on infectiousness of SARS-CoV-2 infections
( Frontiers Media , 2022 , Article)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 ... -
Estimating protection afforded by prior infection in preventing reinfection: Applying the test-negative study design.
( Oxford University Press , 2023 , Article)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 ... -
History of primary-series and booster vaccination and protection against Omicron reinfection
( American Association for the Advancement of Science , 2023 , Article)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 ... -
One Year of SARS-CoV-2: Genomic Characterization of COVID-19 Outbreak in Qatar
( Frontiers , 2021 , Article)Qatar, a country with a strong health system and a diverse population consisting mainly of expatriate residents, has experienced two large waves of COVID-19 outbreak. In this study, we report on 2634 SARS-CoV-2 whole-genome ... -
Population immunity of natural infection, primary-series vaccination, and booster vaccination in Qatar during the COVID-19 pandemic: an observational study
( Elsevier , 2023 , Article)BackgroundWaning 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 ... -
Prevalence of hepatitis B and C viruses among migrant workers in Qatar.
( Springer Nature , 2024 , Article)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 ... -
Protection against Reinfection with the Omicron BA.2.75 Subvariant
( Massachusetts Medical Society , 2023 , Other)The BA.2.75 sublineage of the B.1.1.529 (omicron) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may escape neutralizing antibodies. The BA.2.75 sublineage (primarily the BA.2.75.2 subvariant) ... -
Protection conferred by SARS-CoV-2 infection across a spectrum of reinfection symptoms and severities
( BMJ Publishing Group , 2025 , Article)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 ... -
Protection from previous natural infection compared with mRNA vaccination against SARS-CoV-2 infection and severe COVID-19 in Qatar: a retrospective cohort study
( Elsevier , 2022 , Article)BackgroundUnderstanding 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 ...
