Estimates of Single Dose and Full Dose BNT162b2 Vaccine Effectiveness among USAF Academy cadets, 1 Mar - 1 May 2021

Abstract

Beginning in early March 2021 and continuing through May 2021, the USAF Academy began vaccinating cadets for protection against the SARS-CoV-2 virus with the BNT162b2 (Pfizer-BioNTech) mRNA vaccine. During this period, vaccination of the almost 4200 cadet population increased from 3% to 85% and prevalence of COVID-19 in the cadet population was constant at approximately 0.4% as indicated by weekly surveillance testing. In this study, vaccine effectiveness at preventing infection is estimated by comparing infection risk as a function of time since vaccination. A statistically significant four-fold reduction in infection risk was observed 14 days after the first vaccine dose and an eleven-fold reduction in infection risk was observed in fully vaccinated cadets. Overall, the Pfizer-BioNTech vaccine was 91% (95% confidence interval = 55-99%) effective at preventing infection in healthy young adults (17-26 years of age) in a university setting and military training environment.

Effectiveness of heterologous and homologous covid-19 vaccine regimens: living systematic review with network meta-analysis

“…Twenty seven (6.7%) were protocols, seven (1.7%) were vaccine safety studies, and 370 (91.6%) only examined immunogenicity and reactogenicity in people who were vaccinated. Of the remaining 76 studies, we were able to extract data from 53,2223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374 which gave us a sample size of 100 190 476 participants from 15 countries. Supplementary table 2 presents a summary of the study characteristics.…”

“…We evaluated the risk of bias by following instructions in ROB-2 for randomised controlled trials and ROBINS-I for non-randomised studies 1819. Of the 37 non-randomised studies, 16 were rated to have a moderate risk of bias, mainly because they did not control for confounders such as comorbidities and other baseline characteristics 22323334353738444650566061656874. Nine studies from the same pool were also prone to high selection bias for having an imbalanced proportion of participants of different ages and sexes 223233343537505661.…”

“…Thirty six (7.1%) were protocols, 32 (6.3%) were vaccine safety studies, and 438 (86.6%) only examined immunogenicity and reactogenicity in people who were vaccinated. Of the remaining 106 studies, we were able to extract data from 63, including 10 new studies added to this update, 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 which gave us a sample size of 193 955 736 participants from 20 countries. Supplementary table 2 presents a summary of the study characteristics, with the newly included studies highlighted.…”

“… 19 20 Of the 47 non-randomised studies, 21 were rated to have a moderate risk of bias, mainly because they did not control for confounders such as comorbidities and other baseline characteristics. 23 33 34 35 36 38 39 45 47 51 57 61 62 66 69 75 77 78 81 82 83 Nine studies from the same pool were also prone to high selection bias for having an imbalanced proportion of participants of different ages and sexes. 23 33 34 35 36 38 51 57 62 Five non-randomised studies relied on surveillance data, which were subject to incomplete information, and so received a moderate to severe risk of bias score in the domain of bias due to missing data.…”