Immunogenicity and safety of co-purified diphtheria, tetanus and acellular pertussis vaccine in 6-year-old Chinese children.

In recent years, China has experienced a rapid increase in the number of pertussis cases among children aged 5 to 9. We conducted this phase 4 randomized, controlled trial (NCT05870631) in Zhejiang Province, China, to compare the immunogenicity and safety of co-purified diphtheria, tetanus, and acellular pertussis combined vaccine (co-purified DTaP) to diphtheria and tetanus combined vaccine (DT) in 6-year-old children. Between April 2023 to July 2023, 480 participants were randomized to receive one dose of co-purified DTaP (n = 240) or DT (n = 240). 28 days after vaccination, the seroconversion rates of the co-purified DTaP were 81.20% for anti-PT and 74.36% for anti-FHA, and achieved a significantly higher rate for anti-tetanus compared to the DT vaccine (97.01% vs. 87.05%, P < 0.001). Both vaccines showed 100% seroconversion for anti- diphtheria antibody. For all antibody types, the co-purified DTaP can induced higher geometric mean concentrations. More vaccine-related adverse events were reported with the co-purified DTaP. Most of the severity occurred in Grade 1 and 2. The booster dose of co-purified DTaP vaccination is safe and induces a significant anti-pertussis antibody response, it may be feasible to give a booster dose of co-purified DTaP instead of the recommended DT for 6-year-old children in China.