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Meta-Analysis
. 2021 Nov 14;10(1):132.
doi: 10.1186/s40249-021-00915-3.

Effectiveness and safety of SARS-CoV-2 vaccine in real-world studies: a systematic review and meta-analysis

Qiao Liu #  1 , Chenyuan Qin #  1   2 , Min Liu  3 , Jue Liu  4   5
Affiliations
Meta-Analysis

Effectiveness and safety of SARS-CoV-2 vaccine in real-world studies: a systematic review and meta-analysis

Qiao Liu et al. Infect Dis Poverty. .

Abstract

Background: To date, coronavirus disease 2019 (COVID-19) becomes increasingly fierce due to the emergence of variants. Rapid herd immunity through vaccination is needed to block the mutation and prevent the emergence of variants that can completely escape the immune surveillance. We aimed to systematically evaluate the effectiveness and safety of COVID-19 vaccines in the real world and to establish a reliable evidence-based basis for the actual protective effect of the COVID-19 vaccines, especially in the ensuing waves of infections dominated by variants.

Methods: We searched PubMed, Embase and Web of Science from inception to July 22, 2021. Observational studies that examined the effectiveness and safety of SARS-CoV-2 vaccines among people vaccinated were included. Random-effects or fixed-effects models were used to estimate the pooled vaccine effectiveness (VE) and incidence rate of adverse events after vaccination, and their 95% confidence intervals (CI).

Results: A total of 58 studies (32 studies for vaccine effectiveness and 26 studies for vaccine safety) were included. A single dose of vaccines was 41% (95% CI: 28-54%) effective at preventing SARS-CoV-2 infections, 52% (31-73%) for symptomatic COVID-19, 66% (50-81%) for hospitalization, 45% (42-49%) for Intensive Care Unit (ICU) admissions, and 53% (15-91%) for COVID-19-related death; and two doses were 85% (81-89%) effective at preventing SARS-CoV-2 infections, 97% (97-98%) for symptomatic COVID-19, 93% (89-96%) for hospitalization, 96% (93-98%) for ICU admissions, and 95% (92-98%) effective for COVID-19-related death, respectively. The pooled VE was 85% (80-91%) for the prevention of Alpha variant of SARS-CoV-2 infections, 75% (71-79%) for the Beta variant, 54% (35-74%) for the Gamma variant, and 74% (62-85%) for the Delta variant. The overall pooled incidence rate was 1.5% (1.4-1.6%) for adverse events, 0.4 (0.2-0.5) per 10 000 for severe adverse events, and 0.1 (0.1-0.2) per 10 000 for death after vaccination.

Conclusions: SARS-CoV-2 vaccines have reassuring safety and could effectively reduce the death, severe cases, symptomatic cases, and infections resulting from SARS-CoV-2 across the world. In the context of global pandemic and the continuous emergence of SARS-CoV-2 variants, accelerating vaccination and improving vaccination coverage is still the most important and urgent matter, and it is also the final means to end the pandemic.

Keywords: Effectiveness; Meta-analysis; SARS-CoV-2; Safety; Vaccine.

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Conflict of interest statement

The authors have no conflicts of interest to declare that are relevant to the content of this article.

Figures

Fig. 1
Fig. 1
Flowchart of the study selection
Fig. 2
Fig. 2
Forest plots for the vaccine effectiveness of SARS-CoV-2 vaccines in fully vaccinated populations. A Vaccine effectiveness against SARS-CoV-2 variants; B Vaccine effectiveness against SARS-CoV-2 with variants not mentioned. SARS-CoV-2 severe acute respiratory syndrome coronavirus 2, COVID-19 coronavirus disease 2019, CI confidence interval
See this image and copyright information in PMC

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