Pneumonia causes high rates of hospitalization among adults living in long-term care (LTC) facilities and is a major cause of mortality in this population. Since 2014, pneumococcal conjugate vaccines (PCVs) have been recommended for U.S. adults aged ≥65 years; however, effectiveness of PCVs against all-cause pneumonia hospitalization among adults living in LTC remains unclear. We used Medicare Fee-for-Service claims data to construct an open cohort of beneficiaries aged ≥65 years between September 2014 and December 2019. We estimated 13-valent PCV (PCV13) vaccine effectiveness (VE) by comparing rates of pneumonia hospitalization among PCV13-exposed and PCV13-unexposed time during LTC stays. Discrete-time logistic regression models with generalized estimating equations were used to estimate VE, incorporating time-varying exposures and covariates. Among 3,485,071 beneficiaries meeting the eligibility criteria, the proportion vaccinated with PCV13 increased from 1.1% to 52.7% during the study period. The characteristics of beneficiaries with shorter LTC stays differed from those with longer LTC stays: a lower proportion of beneficiaries aged ≥85 years (LTC stay ≤100 days vs >100 days: 38.5% vs. 48.2%), but a higher proportion with chronic medical conditions (71.4% vs 66.4%), immunocompromising conditions (36.6% vs. 25.2%), and recent hospitalizations (84.1% vs. 74.7%). VE of PCV13-only against all-cause pneumonia hospitalization was 3.8% (95% confidence interval 2.4%-5.2%) overall; 5.6% (3.9%-7.2%) for LTC stays ≤100 days and 0.3% (-2.1%- 2.77%) for LTC stays >100 days. PCV13 reduced the risk of pneumonia hospitalization among this population. Differences in beneficiary characteristics could explain differences in VE by length of LTC stay.
Zielinski et al. (Sat,) studied this question.