RESUMO
BACKGROUNDWaning 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, during a large, rapidly growing Omicron wave. METHODSIn a population of 2,232,224 vaccinated persons with at least two doses, two matched, retrospective cohort studies were implemented to investigate effectiveness of booster vaccination against symptomatic SARS-CoV-2 infection and against COVID-19 hospitalization and death, up to January 9, 2022. Association of booster status with infection was estimated using Cox proportional-hazards regression models. RESULTSFor BNT162b2, cumulative symptomatic infection incidence was 2.9% (95% CI: 2.8-3.1%) in the booster-dose cohort and 5.5% (95% CI: 5.3-5.7%) in the primary-series cohort, after 49 days of follow-up. Adjusted hazard ratio for symptomatic infection was 0.50 (95% CI: 0.47-0.53). Booster effectiveness relative to primary series was 50.1% (95% CI: 47.3-52.8%). For mRNA-1273, cumulative symptomatic infection incidence was 1.9% (95% CI: 1.7-2.2%) in the booster-dose cohort and 3.5% (95% CI: 3.2-3.9%) in the primary-series cohort, after 35 days of follow-up. The adjusted hazard ratio for symptomatic infection was 0.49 (95% CI: 0.43-0.57). Booster effectiveness relative to primary series was 50.8% (95% CI: 43.4-57.3%). There were fewer cases of severe COVID-19 in booster-dose cohorts than in primary-series cohorts, but cases of severe COVID-19 were rare in all cohorts. CONCLUSIONSmRNA booster vaccination is associated with modest effectiveness against symptomatic infection with Omicron. The development of a new generation of vaccines targeting a broad range of variants may be warranted.
RESUMO
BACKGROUNDGrowing 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 BNT162b2 (Pfizer-BioNTech) vaccine in Qatar. METHODSIn a population of 1,531,736 vaccinated persons, two matched retrospective cohort studies were designed and used to investigate differences in mRNA-1273 and BNT162b2 vaccine protection, after the first and second doses, from December 21, 2020 to October 20, 2021. RESULTSAfter dose 1, cumulative incidence of breakthrough infection was 0.79% (95% CI: 0.75-0.83%) for mRNA-1273-vaccinated individuals and 0.86% (95% CI: 0.82-0.90%) for BNT162b2-vaccinated individuals, 21 days post-injection. Adjusted hazard ratio (AHR) for breakthrough infection was 0.89 (95% CI: 0.83-0.95; p=0.001). AHR was constant in the first two weeks at 1, but it declined to 0.67 (95% CI: 0.57-0.77; p<0.001) in the third week after dose 1. AHR for any severe, critical, or fatal COVID-19 was 0.71 (95% CI: 0.53-0.95; p=0.020). After dose 2, cumulative incidence was 0.59% (95% CI: 0.55-0.64%) for mRNA-1273-vaccinated individuals and 0.84% (95% CI: 0.79-0.89%) for BNT162b2-vaccinated individuals, 180 days post-injection. AHR for breakthrough infection was 0.69 (95% CI: 0.63-0.75; p<0.001) and was largely constant over time after dose 2. AHR for any severe, critical, or fatal COVID-19 was 0.37 (95% CI: 0.10-1.41; p=0.147). CONCLUSIONSmRNA-1273 vaccination is associated with lower SARS-CoV-2 breakthrough infection and COVID-19 hospitalization and death than BNT162b2 vaccination, but the number of hospitalizations and deaths was exceedingly small for both vaccines. Both vaccines demonstrated strikingly similar patterns of build-up of protection after the first dose and waning of protection after the second dose.
