Bivalent mRNA-1273.214 vaccine effectiveness in Qatar

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 cohort and 53,901 persons in the no-recent-vaccination cohort. During follow-up, 36 infections were recorded in the bivalent cohort and 211 were recorded in the no-recent-vaccination cohort. None progressed to severe, critical, or fatal COVID-19. Cumulative incidence of infection was 0.53% (95% CI: 0.35-0.79%) in the bivalent cohort and 0.55% (95% CI: 0.47-0.65%) in the no-recent-vaccination cohort, 105 days after the start of follow-up. Incidence during follow-up was dominated by omicron XBB* subvariants including XBB, XBB.1, XBB.1.5, XBB.1.9.1, and XBB.1.9.2. The adjusted hazard ratio comparing incidence of infection in the bivalent cohort to that in the no-recent-vaccination cohort was 0.75 (95% CI: 0.53-1.08). Bivalent vaccine effectiveness against infection was 24.7% (95% CI: -7.0-47.2%). Effectiveness was 16.4% (95% CI: -24.6-47.3%) among persons with no prior infection and 35.3% (95% CI: -12.6-63.4%) among persons with prior infection. mRNA-1273.214 reduced incidence of SARS-CoV-2 infection, but the protection was modest at only ∼25%. The modest protection may have risen because of XBB* immune evasion or immune imprinting effects, or combination of both. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement The authors are grateful for support from the Biomedical Research Program and the Biostatistics, Epidemiology, and Biomathematics Research Core, both at Weill Cornell Medicine-Qatar, as well as for support provided by the Ministry of Public Health, Hamad Medical Corporation, and Sidra Medicine. The authors are also grateful for the Qatar Genome Programme and Qatar University Biomedical Research Center for institutional support for the reagents needed for the viral genome sequencing. Statements made herein are solely the responsibility of the authors. The funders of the study had no role in study design, data collection, data analysis, data interpretation, or writing of the article. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The institutional review boards at Hamad Medical Corporation and Weill Cornell Medicine in Qatar approved this retrospective study with a waiver of informed consent. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes The dataset of this study is a property of the Qatar Ministry of Public Health that was provided to the researchers through a restricted-access agreement that prevents sharing the dataset with a third party or publicly. Future access to this dataset can be considered through a direct application for data access to Her Excellency the Minister of Public Health (). Aggregate data are available within the manuscript and its Supplementary information.