Antibody persistence at 18–20months of age and safety and immunogenicity of a booster dose of a combined DTaP–IPV//PRP∼T vaccine compared to separate vaccines (DTaP, PRP∼T and IPV) following primary vaccination of healthy infants in the People's Republic of China

This study assessed the antibody persistence, and the immunogenicity and safety of a booster dose of a DTaP-IPV//PRP∼T (Pentaxim®, Sanofi Pasteur's AcXim family) combined vaccine and of standalone vaccines one year after primary vaccination in the People's Republic of China. Participants (N=719) previously primed with DTaP-IPV//PRP∼T at 2, 3, 4 months (Group A, N=255), 3, 4, 5 months (Group B, N=233), or DTaP (Wuhan Institute of Biological Products), PRP-T (Act-Hib®) and IPV (Imovax® Polio) at 3, 4, 5 months (Group C, N=231) received boosters of the same vaccines at 18-20 months of age. Seroprotection (SP) and seroconversion (SC) were determined before and 1 month after the booster. Safety was monitored from parental reports. In all groups 87.6-100% of participants had pre-booster protective anti-PRP, -diphtheria, -tetanus and -poliovirus antibody titers; post-booster, all SP rates were 100% and SC was ≥ 80.4% for anti-pertussis titers ≥ 4-fold increase. Reactogenicity was low for each group. These data support the use of the DTaP-IPV//PRP∼T vaccine in the People's Republic of China compared to separate DTaP, IPV, and PRP∼T administration in terms of both safety and immunogenicity.