PHILADELPHIA, PA—Efficacy of 13-valent pneumococcal conjugate vaccine (PCV13) in the prevention of vaccine-type community-acquired pneumonia (VT-CAP) or invasive pneumococcal disease (VT-IPD) declined with age, reported Cornelis H. Van Werkhoven, MD, from Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, Netherlands, at IDWeek 2014.
The impact of age on PCV13 efficacy was tested using data from the CAPiTA trial of 84,496 immunocompetent subjects over 65 years, randomized to PCV13 or placebo (1:1). The effects of vaccination, age, and a vaccine-age interaction on the first episode of VT-CAP or VT-IPD, were assessed using a Cox proportional hazards model. Relative vaccine efficacy by age was calculated by 1 – hazard ratio (HR), and absolute reduction of VT-CAP or VT-IPD was calculated from the model.
The median follow-up time (3.9 years, IQR 3.8–4.8 years), age (71.6 years, IQR 68.1–76.5), and age distribution (12.6% 80+ years, and 3.5% 85+ years), were similar in both vaccine and placebo groups.
PCV13 efficacy was highest among 65 year olds, and then declined with increasing age. In the primary, modified intention-to-treat analysis, 184 VT-CAP or VT-IPD events occurred, and the vaccine-age interaction was significant (P=0.023).
No reduction in antibody responses to PCV13 were seen in subjects >75 years, contrary to previous studies of PCV7.
The number of cases in the oldest age group, >85 years, was too small to draw vaccine efficacy conclusions, but point estimate suggests no vaccine efficacy in this age group.
“Our findings are relevant for cost effectiveness analyses; differences in vaccine efficacy for age groups can be based on empirical data,” concluded Dr. Van Werkhoven