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Review
. 2021 Sep 4;9(9):989.
doi: 10.3390/vaccines9090989.

Safety and Efficacy of COVID-19 Vaccines: A Systematic Review and Meta-Analysis of Different Vaccines at Phase 3

Yu-Jing Fan  1 , Kwok-Hung Chan  2 , Ivan Fan-Ngai Hung  3
Affiliations
Review

Safety and Efficacy of COVID-19 Vaccines: A Systematic Review and Meta-Analysis of Different Vaccines at Phase 3

Yu-Jing Fan et al. Vaccines (Basel). .

Abstract

This systematic review and meta-analysis was conducted to compare the safety and efficacy of 2019 novel coronavirus disease (COVID-19) vaccines according to vaccine platform and severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) infection severity. Articles published between 24 January 2020 and 30 May 2021 were retrieved via a PubMed and EMBASE search. A total of 12 reports on phase-3 clinical trials and observational studies of COVID-19 vaccines were included in the review. In terms of vaccine safety, mRNA vaccines showed more relevance to serious adverse events than viral vector and inactivated vaccines, but no solid evidence indicated that COVID-19 vaccines directly caused serious adverse events. Serious metabolic, musculoskeletal, immune-system, and renal disorders were more common among inactivated vaccine recipients, and serious gastrointestinal complications and infections were more common among viral vector and inactivated vaccine recipients. The occurrence of serious vessel disorders was more frequent in mRNA vaccines. In terms of efficacy, two mRNA vaccine doses conferred a lesser risk of SARS-COV-2 infection (odds ratio: 0.05; 95% confidence interval: 0.02-0.13) than did vaccination with viral vector and inactivated vaccines. All vaccines protected more against symptomatic than asymptomatic cases (risk ratio, 0.11 vs. 0.34), but reduced the risk of severe SARS-COV-2 infection. The COVID-19 vaccines assessed in this study are sufficiently safe and effective. The results indicate that two mRNA vaccine doses prevent SARS-COV-2 infection most effectively, but further research is needed due to the high degree of heterogeneity among studies in this sample. Interventions should be implemented continuously to reduce the risks of infection after one vaccine dose and asymptomatic infection.

Keywords: inactivated vaccines; mRNA vaccines; non-replicating vaccines.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Flowchart for the process and results of study selection in the systematic review.
Figure 2
Figure 2
Forest plot of efficacy of vaccines based on different COVID-19 case definitions.
Figure 3
Figure 3
Adjusted funnel plots to examine publication bias: (a): safety; (b): efficacy after 2 doses; (c): efficacy after 1 dose; (d): severe cases; (e): hospitalization; (f): death (Begg’s funnel plot).
See this image and copyright information in PMC

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