Effectiveness of the 13-valent pneumococcal vaccine against hospitalized community-acquired pneumonia among adults ≥60 years in Madrid-Spain after the COVID-19 pandemic

Few data exist on vaccine effectiveness (VE) of the 13-valent pneumococcal conjugate vaccine (PCV13) against vaccine-type community acquired pneumonia (CAP) among adults, particularly for multiple years post-vaccination. We evaluated PCV13 VE among older adults in Spain right after the emergence of SARS-CoV2. Adults aged ≥60 years hospitalized with CAP were enrolled at five hospitals between March 2021–September 2023. VE was assessed using a test-negative design. Cases were participants from whom PCV13 serotypes were identified from culture or urinary antigen detection assays. All others served as controls. Due to changes in healthcare-seeking behavior, hospital admission, vaccination policies, and CAP etiology during the COVID pandemic period, participants enrolled from March 2021–August 2022 were excluded from analyses. Among 1512 eligible participants, 1241 (82.1 %) were included in the analysis. Median age was 78 years (interquartile range [IQR] 72–85), 34.3 % were immunocompromised and 99.4 % had radiologically-confirmed CAP. Almost half (49.2 %) had received PCV13 of which 33.1 % were vaccinated in 2020 during the COVID-19 pandemic (median time since vaccination: 2.0 years [IQR:2.0–4.2]). Most participants (72.7 %) had previously received the pneumococcal polysaccharide vaccine (PPV23). PCV13 serotypes were identified in 89 (7.2 %) participants, most commonly serotype 3 (56 cases, 62.9 % of PCV13-type CAP). The PCV13 VE against PCV13-type CAP was 26.0 % (−15.21, 52.4 %) overall, 40.9 % (−23.1, 71.6 %) excluding serotype 3 and 51.9 % (−26.0, 81.6 %) among PPV23-naive. Among patients vaccinated <2 years before CAP hospitalization, VE against PCV13-type was 68.9 % (11.9, 89.0 %). In a setting with high serotype 3 prevalence, PCV13 was highly effective in preventing PCV13-type CAP in older adults for two years after vaccination, with lower effectiveness at later time points. Given challenges associated with the pandemic and low statistical power, additional studies are indicated to evaluate serotype-specific duration of protection to inform the need for adult booster vaccinations. • PCV13 was effective in preventing CAP in older adults for 2 years after vaccination. • More than 60 % of PCV13-type CAP was due to serotype 3. • The COVID-19 pandemic and lower sample size limited the validity of the results. • Additional studies are needed to evaluate duration of protection.