Mechanisms of action and immune response for COVID-19 vaccines: A narrative review

Abstract

Background: Corona virus disease – 2019 (COVID-19) is the most important topic in this century with consideration of vaccines as the most important protective tools. In this review we aimed to discuss the different types of COVID-19 vaccines as regarding structures, immunological basics, and currently available forms. We reviewed the available literature about recombinant viral vector, mRNA, inactivated, and protein subunit vaccines. And in the review, we covered mechanisms of action, available forms and whether they lead to lifelong immunity or not. We concluded that it is not yet possible to confirm a lifelong immunity by the available COVID-19 vaccines. With the emergence of SARS-CoV2 new mutant strains, no single vaccine can prove to have a lifelong immunity. Further experiments and research work are needed. We need to conduct research to estimate the prevalence and incidence of COVID-19 patients in already vaccinated people, trials to reach the best ways of giving the vaccines to have the longer protection and the effect of these vaccines on the SARS-CoV-2 new variants.