Efficacy and Safety of COVID-19 Vaccines in Different Variants and Doses: A Systematic Review

Background and aims: Today, with the outbreak of the coronavirus disease 19 (COVID-19) pandemic, we have witnessed many efforts by different countries to produce a vaccine for this disease. Each vaccine has been marketed with different efficiencies, thus this research was designed to determine the efficacy of different types of these vaccines in 2022. Methods: The present research was a systematic review. Researchers surveyed six international databases, including Medline/PubMed, ProQuest, Scopus, EMBASE, Google Scholar, and the ISI Web of Science, in January 2022. After reviewing the titles and abstracts of articles, 60 articles entered the final stage, and their full texts were reviewed based on the study purpose. All the vaccines included in the study were approved by the World Health Organization (WHO) or the Ministry of Health of the manufacturer country in the third phase of the clinical trial. Results: All current vaccination platforms provide adequate protection against severe acute respiratory syndrome coronavirus 2 (SARC-CoV-2) infection and significantly reduce the risk of serious infection. In addition, people who receive two vaccine doses have higher efficacy than those who only receive one dose of each vaccine. The results of the studies demonstrated that the effectiveness of vaccines is different in various groups and countries. According to the results of the reviewed studies, the Pfizer vaccine had an overall effect of 100% on the age group of 12-15 years. The overall effect of the Moderna vaccine varied from 78.6% to 97% in different groups. In general, the available vaccines for COVID-19 are less effective in the Omicron variant. On the other hand, it seems that the COVID-19 vaccines had better efficacy on the alpha variant. Conclusion: Overall, the vaccines used in the COVID-19 pandemic have acceptable efficacy. Although serious side effects caused by the injection of the vaccine have been rarely reported in some studies, it seems that the safety of these vaccines is acceptable in general.