Could a single dose of pneumococcal conjugate vaccine in children be effective? Modeling the optimal age of vaccination.

Using incidence rates from CDC's Active Bacterial Core surveillance and immunogenicity data from the Navajo/Apache trial of pneumococcal conjugate vaccine (PCV), we used Markov modeling to predict the optimal age to give a single dose of PCV. Antibody concentration thresholds of 0.35 and 1.0 mcg/ml were considered protective. Our outcome was vaccine serotype-specific invasive pneumococcal disease (IPD) incidence at 24 months. The models predicted the optimal age to vaccinate is 5-7 months with vaccine-induced immunologic memory and 8-10 months without memory. IPD reduction ranged from 15 to 62%, depending on model parameters. A single PCV dose in infants could prevent substantial IPD.