A comparative analysis of immunogenicity and safety of an enterovirus 71 vaccine between children aged 3-5 years and infants aged 6-35 months

Background: The Sinovac enterovirus 71 (EV71) vaccine has shown good safety, immunogenicity, and efficacy in infants aged 6–35 months, whom are considered as the priority of the target population. However, 3–5 years old children accounted for approximately 30% of HFMD cases and are also worth our attention.

Methods: A randomized, double-blind, placebo-controlled, batch-to-batch consistency clinical trial enrolling 1400 participants aged 6–59 months was performed. We pooled the participants receiving three batches of EV71 vaccine together and then stratified them into the 6–35 months and 3–5 years. The non-inferiority analysis of the geometric mean titer (GMT) of EV71 neutralizing antibody post-vaccination was the primary endpoint.

Results: In the vaccine group, the GMT of 242 children aged 3–5 years was 132.72 (95% CI, 110.3–159.6), which was non-inferior to that generated in 717 infants aged 6–35 months. Following the vaccination, the incidence of adverse reactions was less frequent in children aged 3–5 years (47.0%) than that found in infants aged 6–35 months (60.1%) (p = 0.0026).

Conclusions: Our study indicated that the EV71 vaccine was also safe in children aged 3–5 years, with non-inferior immunogenicity to that in infants aged 6–35 months.