Efficacy of COVID-19 vaccines and virus shedding: systematic review

Abstract

Introduction. SARS-CoV-2 spreads quickly, being characterized by the WHO as a pandemic in March 2020, and can be transmitted through droplets or previously contaminated objects and, therefore, vaccination aimed to reduce infection and contagion by the virus of COVID-19. Objective. To verify the association between the SARS-CoV-2 vaccine and the decrease in viral shedding in adults with COVID-19. Method. The searches for scientific articles took place in the electronic databases MEDLINE (Pubmed), LILACS, SciELO, SCOPUS, WEB OF SCIENCE, without location and language restrictions, in the period from 2020 to 2022. The selection criteria included studies on viral spread of COVID-19 and vaccination against SARS-CoV-2. Results. 7 studies were included, 4 of which point to a positive association between vaccination and the decrease in virus transmission and 3 indicate that the vaccination cycle decreases the chances of serious infection, which may be mild or asymptomatic when transmitted. There was also an inconclusive study, since individuals were not tracked. Conclusion. In the studies evaluated, greater effectiveness in reducing transmission was observed in patients with the complete vaccination cycle and, although efficiency declines after 3 months, booster doses have been used to maintain protection against the virus. In addition, it is noteworthy that the complete vaccination cycle does not prevent the individual from being infected with SARS-CoV-2, however, occasional cases of infection are mild or even asymptomatic.