Vaccination to reduce severe COVID-19 and mortality in COVID-19 patients: a systematic review and meta-analysis

The outbreak of coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in the death of up to 5 million people worldwide, with a mortality rate of approximately 2%. Wearing masks, maintaining social distance, tracking, and isolating close contacts are not sufficient to control the epidemic. The effectiveness of vaccines is affected by the willingness of people to be vaccinated. Therefore, in this review, we aimed to examine the efficacy of different types of vaccines in reducing hospitalization rates, disease severity, and mortality.

We searched five databases (Embase, PubMed, Cochrane, EBSCO, and CEPS) for related research on September 3, 2021. We used a random-effects model for analysis.

Seven studies were identified, involving 1,366,700 participants (689,967 participants in the vaccinated group and 676,733 participants in the non-vaccinated group). There were 292 significant incidents (56 in the vaccinated group and 236 in the non-vaccinated group) with a risk ratio of 0.12 and a 95% confidence interval of 0.040-0.363. Compared with no vaccine, all types of vaccines can effectively prevent the rate of severe illness.

We evaluated whether different brands of vaccines or types of COVID-19 vaccines could prevent the risk of severe illness after diagnosis. The analysis showed that all types of vaccines can effectively prevent severe disease. Implementing epidemic prevention guidelines and obtaining vaccines in different countries can improve vaccine protection and reduce COVID-19-related deaths worldwide.