Determinants of vaccination uptake, and influenza vaccine effectiveness in preventing deaths and hospital admissions in the elderly population; Treviso, Italy, 2014/2015-2016/2017 seasons

Abstract

Seasonal influenza is an important cause of morbidity and mortality, particularly among the elderly population. Determinants of vaccination uptake and its impact on health outcomes in the seasons 2014/ 2015-2016/2017 in elderly living in Treviso area (Veneto Region, NorthEastern Italy) were evaluated. A retrospective cohort study was conducted combining information from several health administrative databases, and multiple Poisson regression models were applied to evaluate the influenza vaccine effectiveness, also adjusting for confounding factors. MF59-adjuvanted trivalent-inactivated vaccine was mainly administered. Data from more than 83,000 elderly people were analyzed by year. Vaccine coverage was about 50%; influenza vaccination uptake was independently associated with older age, male sex, increasing number of underlying chronic conditions, previous pneumococcal vaccination, annual expenses for specialist medical cares, and general practitioner to whom the elderly was in charge. After adjusting for previously described characteristics, vaccination was associated with lower mortality and influenza-related hospitalization rates. Specifically, during influenza season the adjusted incidence rate ratio of death and of influenza-related hospitalizations for vaccinated compared to unvaccinated persons was 0.63 [95% confidence interval (CI) 0.58-0.69, p < .001] and 0.86 (95% CI 0.81-0.91, p < .001), respectively. A similar effectiveness was estimated for death in all age groups (≤74, 75-84, ≥85 years old), whereas a higher effect was found for hospitalizations in subjects aged ≥75 years old. Vaccination was also effective both in males and females. Findings suggest a health benefit of the influenza vaccination in the elderly population. Efforts should be focused on strategies to increase the vaccination uptake as important instrument of prevention.

Impact of Influenza Vaccination on Mortality in the Oldest Old: A Propensity Score-Matched Cohort Study

“…In particular, Voordouw et al showed that annual influenza vaccination and revaccination were associated with a reduction in all-cause mortality risk, similarly in healthy and comorbid subjects of 80 years and older (hazard ratio 0.81, 95% interval confidence: 0.66–1.00; and 0.69, 0.61–0.78, respectively) [ 23 ]. In accordance with our results, a recent study in an elderly Italian population highlighted that influenza vaccine was equally effective for death prevention in all age groups (≤74, 75–84 and ≥85 years old) [ 24 ]. Other authors, in a large cohort study of subjects over 65 years of age, noted a decrease in mortality of 14%, 19% and 1% associated with vaccination during three consecutive winter seasons between 1998 and 2001 [ 25 ].…”

The burden of seasonal influenza in Italy: A systematic review of influenza‐related complications, hospitalizations, and mortality

“…Eight studies reported data on only one season 22,26–29,31,33,37 ; Rizzo et al reported data from 1970 to 2001, 34,35 and Bertolani et al reported data from 2008 to 2015 24 . The other studies reported data on a period of up to four seasons 23,24,30,32,36 . The characteristics of included studies are reported in Table 1.…”

Pneumococcal and Influenza Vaccination Rates and Pneumococcal Invasive Disease Rates Set Geographical and Ethnic Population Susceptibility to Serious COVID-19 Cases and Deaths

“…The third is that the pneumococcal vaccination rate among adults 65 and over has been described as “extremely low in Italy” [ 168 ]. In contrast to Germany, Iceland, Israel, South Korea, Australia, and the U. S., where the over 64 adult pneumococcal vaccination rate is above 50% ( Table 1 ), in the Liguria region of Italy, it was between 26 and 31% [ 168 ]; 24.9% in Calabria (“among the highest in Italy”) [ 170 ]; 20% in the Friuli Venezia Giulia region [ 171 ]; 15.4% in Veneto [ 172 ]; and averaged only 5% per year in each of ten years in the Italian region of Puglia, reaching a cumulative total of no more than 24–30% [ 173 ]. In consequence, even as infant rates of IPD have been falling in recent years, rates among adults over 64 have been increasing and now account for more than two-thirds of all cases in Italy [ 87 , 88 , 151 ].…”