Immunogenicity and safety in infants of a DTwPHib full liquid vaccine

Aim: Combining paediatric vaccines is a rational solution to reduce the number of injections during a single clinical visit, to maintain parents' compliance and to extend vaccine coverage. Different diphtheria, tetanus and whole cell pertussis (DTwP)-containing combination vaccines are licensed and used world-wide. This study assessed the immunogenicity and safety in infants of a combined diphtheria-tetanus-whole cell pertussis-Haemophilus influenzae type b-CRM197 conjugate full liquid vaccine. Methods: The safety and efficacy of a combined ready-to-use liquid vaccine containing diphtheria and tetanus toxoids, cell suspension of Bordetella pertussis and H. influenzae type b-CRM197 conjugate vaccine (DTwPHib) were assessed in infants eligible for the local Expanded Programme on Immunization (EPI) in Valencia, Spain. The comparative group received separate injections of reference vaccines DTwP + Hib. Results: Local and systemic reactions and adverse events were generally mild and similar in the two groups. DTwPHib elicited anti-PR-P antibody titres greater than or equal to0.15 mug ml(-1) in 97% and DTwP + Hib in 94% of infants. Furthermore, 89% of DTwPHib and 78% of DTwP + Hib recipients attained anti-PRP antibody titres greater than or equal to1.0 mug ml(-1), signifying long-term protection. The anti-PRP geometric mean titre was significantly higher in the combined DTwPHib vaccine group (6.65 vs 3.57 mug ml(-1)). In both groups, 99% of infants achieved protective (greater than or equal to0.01 IU ml(-1)) anti-diphtheria antibody levels and all children achieved protective (greater than or equal to0.1 IU ml(-1)) anti-tetanus antibody levels. DTwPHib caused a greater than or equal to2-fold increase in anti-pertactin antibody titres in 91% and a greater than or equal to4-fold increase in 82% of recipients. The corresponding proportions in the DTwP + Hib group were 95% and 90%. DTwPHib induced a greater than or equal to2-fold increase in anti-Aggl2 and 3 antibody levels in 79% and a greater than or equal to4-fold increase in 73% of recipients. The corresponding proportions among DTwP + Hib infants were 85 and 82%. Conclusion: Overall, the combined liquid vaccine DTwPHib is a safe and effective immunogenic vaccine for EPI use in infants.