SARS-CoV-2 vaccination and risk of infectious diseases in hospitalized older patients

AimTo evaluate the incidence of infections and the in-hospital mortality rate in older inpatients vaccinated and unvaccinated against SARS-CoV-2.FindingsSARS-CoV-2 vaccination was associated with a lower likelihood of non-SARS-CoV-2 intra-hospital infections and in-hospital mortality. Cross-reactive immunostimulation may explain these findings.MessageThis research showed the importance of guaranteeing appropriate SARS-CoV-2 vaccination coverage in older population, which could limit not only the incidence and severity of COVID-19 but also the onset of other acute infectious diseases and the risk of in-hospital mortality. PurposeVaccinations, for example flu vaccine, may be a cause of cross-reactive immunostimulation that prevents a larger spectrum of infections. However, whether SARS-CoV-2 vaccinations may also determine this effect is unclear. This study aims, first, to assess the incidence of infections at hospital admission and during the hospitalization in older inpatients vaccinated and unvaccinated against SARS-CoV-2; second, to compare length of hospital stay and in-hospital mortality between vaccinated and unvaccinated individuals.MethodsThis retrospective study included 754 older inpatients admitted to the Geriatrics and Orthogeriatrics Units of the University Hospital of Ferrara (Italy) between March 2021 and November 2021. Sociodemographic and health-related data, and the diagnosis of infections at hospital admission and during hospitalization were collected from medical records.ResultsThe sample's mean age was 87.2 years, 59.2% were females, and 75.5% were vaccinated against SARS-CoV-2. Vaccinated individuals had 36% lower odds of intra-hospital infections (OR = 0.64, 95%CI 0.44-0.94) and 39% lower in-hospital death (HR = 0.61, 95%CI 0.39-0.95), also after adjusting for potential confounders, while no significant results emerged about infections at hospital admission. Considering the hospitalization's endpoints, SARS-CoV-2 vaccination was associated with a lower probability of being transferred to long-term care or other hospital departments than returning home (OR = 0.63, 95%CI 0.40-0.99).ConclusionsIn older inpatients, SARS-CoV-2 vaccination seems to be associated with a lower likelihood of intra-hospital infectious diseases not caused by SARS-CoV-2 and all-cause in-hospital mortality. The vaccination coverage in the older population could limit not only the onset and severity of COVID-19 but also the occurrence of other infectious diseases.