Study on the risk of SARS-CoV-2 infection and subsequent hospital admission and death at different time intervals since the first dose of COVID-19 vaccine administration
On 26 June, an observational study, with no control group, was published evaluating the effectiveness of COVID-19 vaccines in Italy. The study included data from more than 7 million people vaccinated with at least one dose of COVID-19 vaccine. As a reference, 0 to 14 days after the first dose was used, analyzing the risk of SARS-CoV-2 infection after administration of the vaccine.
Fourteen days after vaccination, the risk of infection decreased, with the adjusted risk of infection declining gradually until the period 42–49 days after the first dose, with a reduction of up to 78% (incidence rate ratios
[IRR]: 0.22; 95% CI: 0.21–0.24). Similarly, the risk of hospitalization and death decreased gradually until the period 35-42 days after the first dose, when the estimated risk reduction was 89% (IRR: 0.11; 95% CI: 0.09–0.15) for hospitalization and 93% (IRR: 0.07; 95% CI: 0.04–0.11) for death. The authors conclude that these results support ongoing vaccination campaigns. However, they emphasize the need for complete two-dose vaccine schedules.
Source: Mateo-Urdiales A., Spila Alegiani S., Fabiani M. et al. Risk of SARS-CoV-2 infection and subsequent hospital admission and death at different time intervals since first dose of COVID-19 vaccine administration, Italy, 27 December 2020 to mid-April 2021. Euro Surveill. 2021;26(25):p ii=2100507. https://doi.org/10.2807/15607917.ES.2021.26.25.2100507