We aimed to evaluate 12-y (2012-2024) burden, clinical and microbiological characteristics of Invasive Pneumococcal Disease (IPD) at one large research hospital - IRCCS Fondazione Policlinico San Matteo - in northern Italy, with focus on serotypes' distribution, resistance trends, and vaccination impact on outcomes and costs. The study included 234 IPD cases. Data were obtained from medical records, microbiological reports, and vaccination registries. Statistical analyses included descriptive measures, multivariate regression models for risk factors (adjusted for sex, age group, comorbidities), and comparison of length of stay and costs between vaccinated and unvaccinated patients. Most cases occurred in males aged ≥65. Bacteremia with pneumonia was the most frequent presentation (55.6%). Obesity and splenectomy were associated with higher risk of severe outcome. The most common serotypes overall were 3 and 8. Among vaccinated patients serotypes 15A, 14, 19A, and 15C were more frequent. Macrolide resistance was detected in 26.9% of isolates and beta-lactam resistance in 14.9%. Collectively, 34.5% of cases were caused by serotypes preventable with Pneumococcal Conjugate Vaccine 13 (PCV13), an additional 5.1% by PCV15, 21% by PCV20 and 14.4% by V116 preventable serotypes. Vaccine-preventable serotypes accounted for 64% of cases, mostly (56%) in patients aged ≥65. Vaccinated patients reported shorter hospital stay (median 8 vs 16 d) and lower associated costs (€3313 vs €5101). IPD surveillance is critical to inform prevention strategies. Our findings quantify how much vaccination reduces disease severity and healthcare costs but highlight gaps in vaccine coverage against emerging serotypes due to replacement mechanisms.
Vecchio et al. (Tue,) studied this question.