Bnt162b2

A standardized data extraction form was developed and two investigators (PS and AES) worked independently to extract study details. The following information was extracted: year of study publication, country and time frame, type of vaccine; mRNA-1273 (Moderna); BNT162b2 (Pfizer-BioNTech); Ad26.COV2.S (Janssen), inferential statistical test estimates (vaccine effectiveness or efficacy and its 95% confidence intervals), follow-up time after full vaccination (2-doses for mRNA-127 and BNT162b2 and 1 dose for Ad26.COV2.S), study-level descriptive statistics (mean (SD)/ median (IQR) age in years, proportion (%) female, male and obese), follow-up time (days), and definitions of symptomatic, and severe COVID-19. Authors were contacted for missing or incomplete information. The risk of bias of the included RCTs was evaluated with the Cochrane Collaboration’s Risk of Bias 2 tool (Additional file 1: Table S3) [8 ]. Methodological quality for nonrandomized observational studies was assessed with the Newcastle–Ottawa Scale (NOS) [9 ]. Based on the NOS criteria, we assigned a maximum of 4 stars for selection, 2 stars for comparability, and 3 stars for exposure and outcome assessment. Studies with fewer than 5 stars were considered low quality; 5 to 7 stars, moderate quality; and more than 7 stars, high quality.

We conducted a matched test-negative case-control study between September 6, 2021, and April 22, 2022, in Brazil. The national Covid-19 vaccination campaign started on January 17, 2021, and the administration of booster doses began for the general population on September 6, 2021. The primary series used in Brazil were homologous schemes of Sinovac CoronaVac (two doses), Oxford-AstraZeneca ChAdOx1 nCoV-19 (two doses), Pfizer BNT162b2 (two doses), Janssen Ad26.COV2.S (single dose), and heterologous combinations of the above products in periods of vaccine shortage. All four vaccine products were administered as a homologous or heterologous booster dose. There was no differential recommendation for which vaccine to be administered, except a suggestion for BNT162b2 if available. The booster vaccination followed an age-prioritization scheme. The interval between second and booster doses was initially six months and was subsequently shortened to four months during November 2021 in some states and nationally on December 20, 2021. The proportion of individuals with a primary series of CoronaVac who received a booster dose of Ad26.COV2.S or ChAdOx1 nCoV-19 was small; therefore we limited our analysis to booster doses of CoronaVac and BNT162b2.