Immunogenicity, reactogenicity and safety of a combined DTPa-IPV vaccine compared with separate DTPa and IPV vaccines in healthy Korean infants

Purpose: To compare immunogenicity and reactogenicity of a combined diphtheria-tetanus-acellular pertussis-inactivated poliovirus vaccine (DTPa-IPV, Infanrix™ IPV, GlaxoSmithKline Biologicals) with co-administration of commercially available DTPa and IPV vaccines at separate injection sites (DTPa+IPV). Methods : A total of 458 infants aged 8-12 weeks were randomized to receive three-dose primary vaccination at 2, 4 and 6 months with DTPa-IPV or DTPa+IPV. Blood samples were collected pre and post vaccination for measurement of immune responses. Reactogenicity was assessed following each dose using diary cards. Results : One month post-dose 3, seroprotection rates for anti-diphtheria, anti-tetanus and anti-poliovirus types 1, 2 and 3 were ≥99.5% and vaccine response rates to pertussis antigens were at least 98.6% in both DTPa-IPV and DTPa + IPV groups. Non-inferiority between the groups was demonstrated based on pre-defined statistical criteria. Incidences of both local and systemic symptoms were within the same range across both groups with grade 3 symptoms reported following no more than 4.3% of DTPa-IPV doses and 4.5% of DTPa + IPV doses. Two serious adverse events (both pyrexia) after DTPa-IPV administration were considered vaccine-related. Both infants recovered fully. Conclusion : Combined DTPa-IPV vaccine was immunogenic and well tolerated when used as a three-dose primary vaccination course in Korean infants. DTPa-IPV could be incorporated into the Korean vaccination schedule, reducing the number of injections required to complete primary immunization.