Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2022 Apr 5;17(4):e0266271.
doi: 10.1371/journal.pone.0266271. eCollection 2022.

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

Rajeev Sharma  1 , Abhijith Anand  2
Affiliations

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

Rajeev Sharma et al. PLoS One. .

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.

PubMed Disclaimer

Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Study selection.
This shows the step-wise process of study selection and pre-specified inclusion and exclusion criteria.
Fig 2
Fig 2. Forest plot.
Fig 3
Fig 3. L’Abbe plot to explore heterogeneity.
Fig 4
Fig 4. Association of pandemic prevalence on vaccine efficacy.
Fig 5
Fig 5. Funnel plot.
See this image and copyright information in PMC

References

    1. WHO. Draft landscape and tracker of COVID-19 candidate vaccines 2021 [https://www.who.int/emergencies/diseases/novel-coronavirus-2019/covid-19....
    1. McGill University COVID19 Vaccine Tracker Team. COVID19 Vaccine Tracker website 2021 [https://covid19.trackvaccines.org/.
    1. Shrotri S, Kampmann P. An interactive website tracking COVID-19 vaccine development. The Lancet Global Health. 2021;9(5):E590–E2. doi: 10.1016/S2214-109X(21)00043-7 - DOI - PMC - PubMed
    1. Rogliani P, Chetta A, Cazzola M, Calzetta L. SARS-CoV-2 Neutralizing Antibodies: A Network Meta-Analysis across Vaccines. Vaccines. 2021;9(3):227. doi: 10.3390/vaccines9030227 - DOI - PMC - PubMed
    1. Kyriakidis NC, López-Cortés A, González EV, Grimaldos AB, Prado EO. SARS-CoV-2 vaccines strategies: a comprehensive review of phase 3 candidates. npj Vaccines. 2021;6(1):1–17. - PMC - PubMed