Childhood vaccinations provide an effective method of protection against many diseases. There are multiple advantages to combining vaccines: reducing the number of visits, injections and patient discomfort, increasing compliance, and optimizing prevention. The World Health Organization recommends that routine infant immunization programs include a vaccination against Haemophilus influenzae (H. influenza) type B (HIB) in the combined diphtheria, tetanus, pertussis (DTP)-hepatitis B (HBV) vaccination. The effect of adding a conjugate HIB vaccination to the DTP-HBV vaccine, compared to a separate injection for preventing these diseases, has yet to be assessed.
The objective of this review was to compare the effectiveness of the combined DTP-HBV-HIB vaccine with the separate DTP-HBV and HIB vaccines. No data on clinical outcomes for the primary outcome was found. All included studies reported only on immunogenicity, defined as antibody concentration responses to tetanus, diphtheria, pertussis, hepatitis B and H. influenzae type B and reactogenicity, defined as systematic and local adverse events to vaccination.
Eighteen published randomized or quasi-randomized clinical trials, comparing vaccination with any combined DTP-HBV-HIB vaccine with or without three types of inactivated poliovirus (IPV) or concomitant oral polio vaccine (OPV) given in any dose, preparation or time schedule, compared with separate vaccines or placebo, administered to infants aged up to two years, were included. In two immunological responses the combined vaccine achieved lower responses than the separate vaccines for HIB and HBV. No significant differences in immunogenicity were found for pertussis, diphtheria, polio and tetanus. Serious adverse events were comparable. Minor adverse events were more common in children given the combined vaccine.
Overall, the level of evidence provided by the studies was low, and we could not conclude that the immune responses elicited by the combined vaccine are equivalent to the separate injections. The combined vaccine did not result in a significant increase in the incidence of serious adverse events, but caused more minor reactions.