The effect of pandemic prevalence on the reported efficacy of SARS-CoV-2 vaccines

Rajeev Sharma and Abhijith Anand

PLOS ONE, 2022, vol. 17, issue 4, 1-14

Abstract: The efficacy of SARS-CoV-2 vaccines reported in Phase 3 trials varies from ~45% to ~95%. This study tests the hypothesis that the observed variation in efficacy of SARS-CoV-2 vaccine candidates can be explained by the prevalence of the COVID-19 pandemic at trial sites. To test the proposed hypothesis, we conducted a systematic search following PRISMA guidelines. Our search resulted in 8 vaccine candidates that had reported efficacy data from a total of 20 Phase 3 trials, representing a total of 221,968 subjects, 453 infections across the vaccinated groups and 1,554 infections across the placebo groups. We use meta-regression models to analyse the potential associations between prevalence of COVID-19 pandemic at trial sites and efficacy of the reported SARS-CoV2 vaccines. The overall estimate of the risk-ratio is 0.24 (95% CI, 0.17–0.34, p ≤ 0.01), with a high degree of heterogeneity (τ2 = 0.50, I2 = 88.73%). Our meta-regression analysis with pandemic prevalence as the predictor explains almost half the variance in risk ratios across trials (R2 = 49.06%, p ≤ 0.01). This study finds that efficacy of SARS-CoV-2 vaccines reported in Phase 3 trial declines as pandemic prevalence at trial sites increases. Trials conducted in locations with low pandemic prevalence reported higher efficacies as compared to trials conducted in high pandemic prevalence locations.

Date: 2022
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Persistent link: https://EconPapers.repec.org/RePEc:plo:pone00:0266271

DOI: 10.1371/journal.pone.0266271

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