Rotavirus infections have been linked to 40–50% of all hospitalized acute gastroenteritis cases in Japanese children under the age of five. In Japan, Rotarix containing the live attenuated human rotavirus RIX4414 strain (HRV) has been approved for babies since 2011. In Japan, rotavirus vaccination is voluntary, but diphtheria, pertussis, tetanus, and inactivated poliovirus (DPT-IPV) vaccine is part of the national regular immunization program. The immunogenicity and safety of the DPT-IPV vaccination delivered concurrently or staggered with the liquid HRV vaccine in healthy Japanese babies were assessed in an open-label, randomized, controlled, multicenter trial. A total of 292 babies aged 6–12 weeks were randomly allocated to receive DPT-IPV and HRV vaccines either concurrently or sequentially. Immune responses to the DPT-IPV vaccine were measured one month after the third dose of the DPT-IPV vaccine by assessing post-vaccination serum antibody titers/concentrations to each antigen. In both groups, seroprotection/seropositivity against diphtheria, pertussis, tetanus, and poliovirus type 1, 2, and 3 antigens was 92.8 percent or higher. In terms of immunogenicity, DPT-IPV vaccination delivered concurrently with HRV vaccine was demonstrated to be non-inferior to DPT-IPV vaccine administered sequentially. 

The safety profile of the two vaccination groups was comparable, with no vaccine-related severe adverse events, fatalities, or instances of intussusception. These findings support the use of HRV vaccination in conjunction with DPT-IPV immunization in Japan.