DOI: https://doi.org/10.21203/rs.3.rs-1227382/v1
Background: We provide here an analysis of effectiveness of primary coronavirus disease 2019 (COVID-19) vaccination and COVID-19 vaccine booster doses in preventing severe acute respiratory syndrome coronavirus 2 (COVID-19) infection.
Methods: We retrieved information on COVID-19 vaccination and newly diagnosed cases of SARS-CoV-2 infection from the weekly official report of the Italian National Institute of Health (Istituto Superiore di Sanità , ISS; Last available update, January 1, 2022).
Results: At the time of our analysis, 39.9 million people completed a primary COVID-19 vaccination cycle, of whom 13.6 million (34.0%) <5 months from the last dose, whilst 5.7 million had also received COVID-19 vaccine booster doses. The risk of SARS-CoV-2 infection was 71% (OR, 0.29; 95%CI, 0.29-0.29) and 86% (OR, 0.14; 95%CI, 0.14-0.14) lower in people who received primary vaccination <5 months and booster doses <5 months compared to the unvaccinated population, but was also half (OR, 0.49; 95%CI, 0.48-0.49) in those who received booster doses <5 months compared to those who completed the primary vaccination <5 months.
Conclusions: These results attest that COVID-19 vaccines not only reduce the risk of developing severe illness in patients with SARS-CoV-2 infection, but shall also be considered reliable and effective means to limit virus circulation within the general population.