Background and objective:
Prevention Unit from GD Welfare Lombardy evaluated COVID vaccination efficacy among elderly patients who reside in Lombardy long-term care facilities. Aim of the study was to observe the trend of COVID infections and related hospitalizations and deaths in the trimester September-November 2022, in relation to the number of anti-COVID vaccination shots received.

Methods:
Population included 55,478 patients. Data were extracted from regional disease reporting application “tableau server"". Based on number of inoculations received, patients were stratified and four categories were identified: unvaccinated, vaccinated with less than three doses (patients who did not complete the primary cycle were excluded), vaccinated who received a third dose (1st booster shot), vaccinated who received a fourth dose (2nd booster shot). Only mRNA-based vaccines were employed. For each category, different outcomes were assessed: infection rate, hospitalization rate, mortality rate.

Results:
138 out of 521 unvaccinated became infected (26,5%); infection rate in vaccinated resulted 7,3% for patients with primary cycle completed (120/1643), 11,1% for vaccinated with 1st booster shot (1085/9718) and 11,4% among patients who received a 2nd booster dose (4970/43422). Overall infection rate was significantly higher in unvaccinated (26,5%) than vaccinated (0,11%) cohort. Among unvaccinated patients, 6 were hospitalized (1,2%) and 15 died (2,9%). Hospitalization rate in vaccinated was 0,3%, mortality rate 0,5%: in patients with primary cycle completed, 5 hospitalizations (0,3%) and 8 deaths (0,5%) were counted. Hospitalization rate was 0,4% and 0,2%, respectively, in 1st boost (n=35) and 2nd boost cohorts (n=108). Furthermore, mortality rate resulted 0,1% among vaccinated with 1st booster shot (n=67) and slightly increased to 0,4% among 2nd booster group (n=198).

Conclusion:
Infection, hospitalization and mortality rates significantly decrease as patients complete at least the primary vaccination cycle. Data confirm the importance of COVID-19 vaccination campaign as prevention tool in elderly patients residing in long-term care facilities.