Respiratory tract infections are among the leading causes of death worldwide and many of these infections are preventable through vaccination. One of the most important bacteria from an etiological and mortality point of view regarding respiratory and systemic infections is the gram-positive Streptococcus pneumoniae. Four types of vaccines are currently available for this pathogen: three pneumococcal conjugate vaccines (PCV13, PCV15, and PCV20) and one polysaccharide vaccine (PPSV23). In Italy, people over 65 years of age and people suffering from chronic pathologies with effects on the immune system would be advised to be vaccinated with the pneumococcal conjugate vaccine and with the polysaccharide vaccine as a second dose.

However, there are no data available in Italy on vaccination coverage in these population categories and above all the vaccination rates in patients who have a history of an episode of invasive pneumococcal infection are not known. The aim of the study is to measure how many patients are vaccinated for S. pneumoniae after hospitalization for a systemic pneumococcal infection in order to understand patients' awareness of preventing this infection after receiving a first diagnosis.

Inclusion Criteria:

• Patients over 18 years old;
• Patients hospitalized at the Manzoni Hospital in Lecco or at the San Raffaele Hospital in Milan with invasive pneumococcal infection in the period between 01/01/2015 and 31/12/2019;
• Presence of a positive culture test for S. pneumoniae on blood cultures and/or liquor;
• Patients whose discharge letter or clinical documentation relating to the infectious episode is available;
• Patients whose vaccination record can be consulted (on paper or on SIAVR) and whose vaccination history is available before and after hospitalization.

Exclusion Criteria:

• Patients with positive urinary antigen for S. pneumoniae as the only microbiological finding;
• Patients whose vaccination history or vaccination records are not available.

A retrospective multicenter study is planned on patients admitted to the Alessandro Manzoni Hospital in Lecco and the San Raffaele Hospital in Milan with a diagnosis of systemic pneumococcal infection from 01/01/2015 to 12/31/2019 before the SARS pandemic -CoV-2.

All patients admitted with a diagnosis of invasive pneumococcal infection defined by positive blood or CSF cultures for S. pneumoniae by the microbiology laboratory were enrolled.