Safety and immunogenicity of inactivated human Rotavirus vaccine in young children and infants: a randomized, placebo-controlled, double-blind, phase I clinical trial.

Inactivated rotavirus vaccines (IRV) are an effective approach for providing protection against the virus. This double-blind, randomised, placebo-controlled, dose-escalation phase I trial evaluated the safety and immunogenicity of IRV in 288 healthy children aged 2-71 months without prior rotavirus vaccination or HIV infection. We stratified participants by age (7-71 months and 2-6 months) and schedule (2 or 3 doses), before randomising them 3:1 to receive one of three antigen doses (80, 160, or 320 ELISA Unit [EU]), or aluminium adjuvanted placebo. The primary endpoints included adverse reactions/events within 30 min post-dose, adverse reactions/events during days 0-7 and 8-28/30 post-dose, and serious adverse events (SAEs) 6 months after the full course. The secondary endpoints were neutralizing antibody (NTA) geometric mean titres (GMT) and seroconversion rates (≥4-fold rise) at day 28 post-final dose. IRV was well tolerated, with no vaccine-related SAEs in any of the cohorts; we observed clinically manageable transient mild-to-moderate fever in the high dose infant group. Dose-dependent increases in NTA and IgG antibody responses were observed across all cohorts. In the 3-dose infant group, the 320 EU dose yielded a GMT of 551.98 (95% CI 338.39 ~ 900.40) compared to 36.17 for placebo, and a seroconversion rate of 83.33% (vs. 10.00% for placebo); the 3-dose schedule outperformed the 2-dose regimen. Our findings confirm that IRV has a favourable safety and immunogenicity profile. This trial is registered with ClinicalTrials.gov (NCT04626856).