Effectiveness of 13-valent pneumococcal conjugate vaccine against medically-attended lower respiratory tract infection and pneumonia among older adults

Importance: In 2014, the US Advisory Committee on Immunization Practices (ACIP) extended existing pneumococcal vaccination recommendations for adults aged [≥]65 years to include 13-valent pneumococcal conjugate vaccine (PCV13), primarily to prevent non-bacteremic pneumonia. Objective: To determine PCV13 effectiveness against all-cause inpatient plus outpatient medically-attended lower-respiratory tract infection (LRTI) and pneumonia among US older adults. Design: Prospective, open cohort study following participants from 2016 to 2019. We conducted analyses in a self-matched framework, comparing outcomes during participants' follow-up periods before and after receipt of PCV13. Setting: Kaiser Permanente Southern California (KPSC) integrated healthcare delivery system. Participants: Adults aged [≥]65 years who received PCV13 between 2016-2019. Exposures: Receipt of PCV13 at ages [≥]65 years, concordant with ACIP guidelines. Main outcomes and measures: We estimated the adjusted hazards ratio (aHR) for first LRTI and pneumonia episodes during each respiratory season, comparing PCV13-exposed and PCV13-unexposed time at risk for each participant using a self-matched inference framework. We computed aHR estimates using Cox proportional hazards models. We defined vaccine effectiveness (VE) as (1-aHR)*100%. We also estimated PCV13-attributable absolute reductions in incidence of LRTI and pneumonia. Results: Observations were available both before and after PCV13 receipt for 42,700 participants. Among these individuals, 1,419 experienced LRTI and 969 experienced pneumonia over approximately 26,000 combined years of follow-up before PCV13 receipt; 3,849 experienced LRTI and 2,727 experienced pneumonia over approximately 74,000 combined years of follow-up after PCV13 receipt. In adjusted analyses, VE was 9.5% (95% confidence interval: 2.2% to 16.3%) against all-cause medically-attended LRTI and 8.8% (-0.2% to 17.0%) against all-cause medically-attended pneumonia. In contrast, we did not identify evidence of protection against LRTI and pneumonia following receipt of 23-valent pneumococcal polysaccharide vaccine. We estimated that PCV13 prevented 0.7 (0.2 to 1.4) and 0.5 (0.0 to 1.0) cases of LRTI and pneumonia, respectively, per 100 vaccinated persons annually. Over a five-year time horizon, one case of LRTI and pneumonia, respectively, was prevented for every 27 (14 to 116) and 42 (-97 to 268) individuals receiving PCV13. Conclusions and relevance: PCV13 vaccination among older adults reduced the burden of medically-attended respiratory illness in this population.