Impact of COVID-19 vaccination on the risk of SARS-CoV-2 infection and hospitalization and death in Italy (27.12.2020 - 14.07.2021). English version of the ISS report - ISS (EN)

Key Points

• This is the third report on the combined analysis of data from the Italian National Vaccination Registry and the COVID-19 integrated surveillance system. This activity is pursuant to Decree-law No. 2 of 14 January 2021 regulating the information systems that are instrumental to implementing the national strategic vaccination plan for the prevention of SARS-CoV-2 infections (Art. 3, Paragraph 7).
• The aim of the assessment is to analyse the impact of COVID-19 vaccination on the risk of being infected, hospitalized, admitted to an Intensive Care Unit, or dying from SARS-CoV-2, and the persistence of vaccine-induced protection over time. The data contained in this report are complementary to the vaccine efficacy estimates obtained with different methods and reported in the weekly bulletin “COVID19 Epidemic. National Update” available on the ISS EpiCentro Website.
• This report takes into consideration over 27 million people (representing half of the Italian population ≥12 years of age) who received at least one dose of a COVID-19 vaccine. The risk of being diagnosed with a SARS-CoV-2 infection is assessed after over 170 days since the first vaccine dose administration.
• In the study period, the incidence of a COVID-19 diagnosis decreases from 1.2 per 10,000 person-days in the first 14 days after the first dose (reference period, during which risk is comparable to non-vaccinated individuals) to 0.6 in incompletely vaccinated persons and to 0.3 in those that are completely vaccinated. The risk of receiving a COVID-19 diagnosis decreases progressively starting two weeks after the first dose administration, reaching a risk reduction rate greater than 95% at the end of the observation period. The risk of a Covid diagnosis continues to remain very low over 170 days after receiving a first dose.
• The incidence rate of hospitalization in persons vaccinated before 16 May 2021 decreases from 0.27 (per 10,000 person-days) in the first 14 days after the first dose, to 0.09 in incompletely vaccinated persons and to 0.03 in those completely vaccinated. In the first 14 days after the first dose of vaccine, a higher incidence is observed in the ≥80 years age group compared to people aged below 40 (respectively 0.70 versus 0.05/10,000 person days); this difference narrows down in those fully vaccinated (0.06 vs 0.01).
• The incidence rate of mortality following a COVID-19 diagnosis among people vaccinated before 16 May 2021 decreases from 0.08 per 10,000 person-days in the first 14 days after receipt of a first dose, to 0.01 in completely vaccinated individuals. In the latter group, the incidence does not differ substantially in terms of age, gender, geographical area, calendar period and brand, and always remains below 0.02 per 10,000 person-days.
• Vaccines are confirmed to be beneficial in all age groups, in both males and females, also over the longer observation period (170 days).
• The stratified analysis by brand suggests, for all vaccines, a reduction of the risk of infection, hospitalization, admission to an intensive care unit, and of mortality, starting from the second week after the first or -single dose administration; in case of a two-dose vaccine schedule, a further risk reduction is observed after administration of the second dose, and no loss of efficacy over time was observed.