Primary COVID-19 vaccine cycle and booster doses efficacy: analysis of Italian nationwide vaccination campaign

We provide here an updated analysis of primary COVID-19 vaccination and vaccine booster doses efficacy, emerging from the ongoing Italian nationwide COVID-19 vaccination campaign. Primary COVID-19 vaccination efficacy was 76-92% within 6 months, decreasing to 34-80% after 6 months. Administration of vaccine booster doses decreased SARS-CoV-2 infections by 65%, COVID-19 related hospitalizations and deaths by 69% and 97% compared to vaccine efficacy after 6 months, but also decreased SARS-CoV-2 infections by 39% compared to vaccine efficacy within 6 months. These results suggest that COVID-19 vaccine booster doses are important for restoring vaccine efficacy and further limiting virus circulation.

Automated summary

This article provides an updated analysis on the efficacy of primary COVID-19 vaccination and vaccine booster doses, based on the ongoing nationwide vaccination campaign in Italy. The study found that the efficacy of primary COVID-19 vaccination ranged from 76-92% within 6 months, but decreased to 34-80% after 6 months. Administration of vaccine booster doses reduced SARS-CoV-2 infections by 65%, COVID-19 related hospitalizations and deaths by 69% and 97% respectively compared to the efficacy after 6 months, and also reduced SARS-CoV-2 infections by 39% compared to the efficacy within 6 months. These results suggest the importance of COVID-19 vaccine booster doses in restoring efficacy and further limiting virus circulation.