Adverse events following COVID-19 vaccination: A systematic review and meta-analysis

•MRNA vaccines are associated with greater risk of adverse events (AES) following immunization.•Different vaccine modalities are different regarding the level of AES contributing to immunization.•Most of the studies reported the result of the clinical trials phase I and II together. High speed of COVID-19 vaccination has raised some concerns about the safety of the new vaccines. It is of a great importance to perform a review of the safety and efficacy of the COVID-19 vaccines. Two International electronic databases (PubMed, ISI) were searched for clinical trials reporting efficacy and safety of COVID-19 vaccines compared to control group. Pooled risk ratio (RR) for total, systemic and local adverse events following immunization was calculated for different vaccine modalities. The pooled RRs of total adverse reactions for Inactivated, mRNA, and vector vaccines were 1.46 (95% CI: 1.19–1.78), 2.01 (95% CI: 1.82 – 2.23), and 1.65 (95% CI: 1.31 – 2.32) respectively. The pooled RR for occurrence of systemic adverse reactions following immunization for different vaccine modalities was 1.13 (95% CI: 0.79 – 1.61), 1.53 (95% CI 1.08 – 2.16), 1.58 (95% CI: 1.13 – 1.90), 0.72 (95% CI: 0.34 – 1.55), and 1.62 (95% CI: 1.39 – 1.89) for inactivated vaccine, mRNA, vector, DNA, and protein subunit vaccines respectively. The pooled RR of local adverse event following immunization with inactivated vaccine, mRNA vaccine, vector vaccine, DNA vaccine, and protein subunit vaccine was 2.18 (95% CI: 1.32 – 3.59), 4.96 (95% CI: 4.02 – 6.11), 1.48 (95% CI: 0.88–2.50) 1.04 (95% CI: 0.12–8.75), and 4.09 (95% CI: 2.63–6.35) respectively. mRNA vaccines are associated with greater risk of adverse events following immunization. However, at the present moment the benefits of all types of vaccines approved by WHO, still outweigh the risks of them and vaccination if available, is highly recommended.