No abstract

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 mRNA-1273 (Moderna) vaccines in Qatar, as compared with protection conferred by the two-dose primary series, is unclear. Methods We conducted two matched retrospective cohort studies to assess the effectiveness of booster vaccination, as compared with that of a two-dose primary series alone, against symptomatic SARS-CoV-2 infection and Covid-19–related hospitalization and death during a large wave of omicron infections from December 19, 2021, through January 26, 2022. The association of booster status with infection was estimated with the use of Cox proportional-hazards regression models. Results In a population of 2,239,193 persons who had received at least two doses of BNT162b2 or mRNA-1273 vaccine, those who had also received a booster were matched with persons who had not received a booster. Among the BNT162b2-vaccinated persons, the cumulative incidence of symptomatic omicron infection was 2.4% (95% confidence interval [CI], 2.3 to 2.5) in the booster cohort and 4.5% (95% CI, 4.3 to 4.6) in the nonbooster cohort after 35 days of follow-up. Booster effectiveness against symptomatic omicron infection, as compared with that of the primary series, was 49.4% (95% CI, 47.1 to 51.6). Booster effectiveness against Covid-19–related hospitalization and death due to omicron infection, as compared with the primary series, was 76.5% (95% CI, 55.9 to 87.5). BNT162b2 booster effectiveness against symptomatic infection with the delta (or B.1.617.2) variant, as compared with the primary series, was 86.1% (95% CI, 67.3 to 94.1). Among the mRNA-1273–vaccinated persons, the cumulative incidence of symptomatic omicron infection was 1.0% (95% CI, 0.9 to 1.2) in the booster cohort and 1.9% (95% CI, 1.8 to 2.1) in the nonbooster cohort after 35 days; booster effectiveness against symptomatic omicron infection, as compared with the primary series, was 47.3% (95% CI, 40.7 to 53.3). Few severe Covid-19 cases were noted in the mRNA-1273–vaccinated cohorts. Conclusions The messenger RNA (mRNA) boosters were highly effective against symptomatic delta infection, but they were less effective against symptomatic omicron infection. However, with both variants, mRNA boosters led to strong protection against Covid-19–related hospitalization and death. (Funded by Weill Cornell Medicine–Qatar and others.)

No abstract

In a randomized clinical trial, the mRNA-1273 (Moderna) vaccine had a reported efficacy of 94.1% in preventing symptomatic coronavirus disease 2019 due to infection with wild-type variants 1 . The first immunization using this vaccine in Qatar was recorded on 28 December 2020, but mass vaccination did not start until late February 2021 with the accelerated arrival of vaccine shipments. As the vaccination campaign was scaled up, the country experienced two back-to-back severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) waves that were triggered by the introduction and expansion of the B.1.1.7 (Alpha 2 ) and B.1.351 (Beta 2 ) variants 3 . This created a unique epidemiological opportunity to assess the real-world effectiveness of this vaccine against infection with these variants of concern, as well as against severe forms of COVID-19 disease. ResultsStudy population. Between 28 December 2020 and 10 May 2021, 256,037 individuals in Qatar received at least one dose of the mRNA-1273 vaccine and 181,304 completed the two-dose regimen. Among those with a vaccination record, the median dates at first and second dose were 5 and 29 April 2021, respectively. The median time elapsing between the first and second doses was 28 days (interquartile range (IQR): 28-29 days), with 94.6% of individuals receiving their second dose ≤30 days after the first dose.Flowcharts describing the population selection process for investigation and estimation of vaccine effectiveness are presented in Extended Data Figs. 1-3, and the demographic characteristics of the sample for each outcome of vaccine effectiveness are presented in Table 1. Median age in the study sample for estimation of vaccine effectiveness against infection with B.1.1.7 was 31 years (IQR: 19-38), against infection with B.1.351 was 32 years (IQR: 25-39) and against severe, critical or fatal disease was 43 years (IQR: 37-51). Of note is that Qatar has a young and diverse demographic, where only 9% of its resident population are >50 years of age and 89% are expatriates from >150 countries 4,5 .

BACKGROUND: Waning of vaccine protection against SARS-CoV-2 infection or COVID-19 disease is a concern. This study investigated persistence of BNT162b2 (Pfizer-BioNTech) vaccine effectiveness against infection and disease in Qatar, where the Beta and Delta variants have dominated incidence and PCR testing is done at a mass scale. METHODS: A matched test-negative, case-control study design was used to estimate vaccine effectiveness against SARS-CoV-2 infection and against any severe, critical, or fatal COVID-19 disease, between January 1, 2021 to August 15, 2021. RESULTS: Estimated BNT162b2 effectiveness against any infection, asymptomatic or symptomatic, was negligible for the first two weeks after the first dose, increased to 36.5% (95% CI: 33.1-39.8) in the third week after the first dose, and reached its peak at 72.1% (95% CI: 70.9-73.2) in the first five weeks after the second dose. Effectiveness declined gradually thereafter, with the decline accelerating ≥15 weeks after the second dose, reaching diminished levels of protection by the 20th week. Effectiveness against symptomatic infection was higher than against asymptomatic infection, but still waned in the same fashion. Effectiveness against any severe, critical, or fatal disease increased rapidly to 67.7% (95% CI: 59.1-74.7) by the third week after the first dose, and reached 95.4% (95% CI: 93.4-96.9) in the first five weeks after the second dose, where it persisted at about this level for six months. CONCLUSIONS: BNT162b2-induced protection against infection appears to wane rapidly after its peak right after the second dose, but it persists at a robust level against hospitalization and death for at least six months following the second dose.