Abstract
OBJECTIVES: Pneumococcal serotype 4 illness surged among some US Native American and homeless populations. The impact of potential serotype 4 rate increases on US adult pneumococcal conjugate vaccine (PCV) options is unclear. STUDY DESIGN: Decision analysis. METHODS: A Markov model estimated differences in public health effects in US 50- and 65-year-old cohorts between 21-valent PCV (PCV21), which does not contain serotype 4, and 20-valent PCV (PCV20), which does contain it, tracking outcome differences resulting from serotype 4 illness rate increases from 0 to 6 per 100,000 over baseline annual rates. CDC data informed vaccine serotype-specific pneumococcal disease risks. Model parameters were varied in deterministic and probabilistic sensitivity analyses. RESULTS: At a baseline serotype 4 disease risk of <1 per 100,000, PCV21 resulted in fewer lifetime pneumococcal disease cases in 50- and 65-year-olds compared to PCV20 and gained lifetime quality-adjusted life years. In 50-year-olds, absolute increases in serotype 4 illness rates of ≥3 per 100,000 and in 65-year-olds increases >5 per 100,000 (i.e., to levels not observed in US national or regional data) were necessary for PCV21 to become unfavorable. Results were robust in sensitivity analyses. CONCLUSIONS: PCV21 was favored in US 50- and 65-year-olds unless potentially implausible general population increases in serotype 4 illness occur.