Efficacy and Effectiveness of SARS-CoV-2 Vaccines: A Systematic Review and Meta-Analysis

Abstract

The coronavirus disease 2019 (COVID-19) pandemic has threatened global health and prompted the need for mass vaccination. We aimed to assess the efficacy and effectiveness of COVID-19 vaccines to prevent mortality and reduce the risk of developing severe disease after the 1st and 2nd doses. From conception to 28 June 2021, we searched PubMed, Cochrane, EBSCO, Scopus, ProQuest, Web of Science, WHO-ICTRP, and Google Scholar. We included both observational and randomized controlled trials. The pooled vaccine efficacy and effectiveness following vaccination, as well as their 95 percent confidence intervals (CI), were estimated using the random-effects model. In total, 22 of the 21,567 screened articles were eligible for quantitative analysis. Mortality 7 and 14 days after full vaccination decreased significantly among the vaccinated group compared to the unvaccinated group (OR = 0.10, ([95% CI, 0.04-0.27], I² = 54%) and (OR = 0.46, [95% CI, 0.35-0.61], I² = 0%), respectively. The probability of having severe disease one or two weeks after 2nd dose decreased significantly (OR = 0.29 [95% CI, 0.19-0.46], I² = 25%) and (OR = 0.08 [95% CI, 0.03-0.25], I² = 74%), respectively. The incidence of infection any time after the 1st and 2nd doses diminished significantly (OR = 0.14 [95% CI, 0.07-0.4], I² = 100%) and (OR = 0.179 [95% CI, 0.15-0.19], I² = 98%), respectively. Also, incidence of infection one week after 2nd dose decreased significantly, (OR = 0.04, [95% CI (0.01-0.2], I² = 100%). After meta-regression, the type of vaccine and country were the main predictors of outcome [non-mRNA type, ß = 2.99, p = 0.0001; country UK, ß = -0.75, p = 0.038; country USA, ß = 0.8, p = 0.02]. This study showed that most vaccines have comparable effectiveness, and it is purported that mass vaccination may help to end this pandemic.

Keywords: COVID-19 vaccine; SARS-CoV-2; effectiveness; efficacy; meta-anlysis; mortality; systematic review.

Figure 1

PRISMA flow chart of studies screened and a Summary of included studies in the qualitative analysis.

Figure 2

Funnel plot of studies that reported mortality after 2nd dose among vaccinated population.

Figure 3

Quality assessment of RCT studies.

Figure 4

(A) Mortality 7 days after the 2nd dose of COVID-19 vaccination. (B) Mortality 14 days after 2nd dose of COVID-19 vaccination.

Figure 5

(A) Severe COVID-19 infection 7 days after 2nd dose of vaccination. (B) Severe COVID-19 infection 7 days after 1st dose of vaccination.

Figure 6

(A) Incidence of SARS-CoV-2 infection either symptomatic or asymptomatic within 14 days of 1st dose of vaccination. (B) Incidence of asymptomatic SARS-CoV-2 within 14 days of 1st dose of vaccination.

Figure 7

Incidence of SARS-CoV-2 infection either symptomatic or asymptomatic within 21 days after the 1st dose of vaccination.

Figure 8

Incidence of all SARS-CoV-2 cases after 1st dose of vaccination.

Figure 9

(A) Incidence of SARS-CoV-2 infection either symptomatic or asymptomatic within 7 days of 2nd dose of vaccination. (B) Incidence symptomatic SARS-CoV-2 within 7 days of 2nd dose of vaccination.

Figure 10

Incidence of SARS-CoV-2 infection either symptomatic or asymptomatic within 14 days of 2nd dose of vaccination.

Figure 11

(A) Incidence of SARS-CoV-2 infection either symptomatic or asymptomatic after 7 days of 2nd dose of vaccination. (B) Incidence of symptomatic SARS-CoV-2 after 7 days of 2nd dose of vaccination. (C) Incidence of asymptomatic SARS-CoV-2 after 7 days of 2nd dose of vaccination.

Figure 12

(A) Incidence of SARS-CoV-2 infection either symptomatic or asymptomatic after 14 days of 2nd dose of vaccination. (B) Incidence of symptomatic SARS-CoV-2 after 14 days of 2nd dose of vaccination. (C) Incidence of asymptomatic SARS-CoV-2 after 14 days of 2nd dose of vaccination.

Figure 13

All cases of confirmed SARS-CoV-2 infection reported after 2nd dose of vaccination regardless of the duration.