Immunogenicity and reactogenicity following primary immunisation with a combined DTaP-HBV vaccine and a Haemophilus influenzae type B vaccine administered by separate or mixed injection

Objectives: The aim of this open, randomised, multicentre trial was to evaluate the immunogenicity and reactogenicity of the tetravalent diphtheria-tetanus-acellular pertussis-hepatitis B (DTaP-HBV) vaccine when given either as a mixed or as a separate concomitant injection with the Haemophilus influenzae type b (Hib) vaccine at 3, 5 and 11 months of age. Methods: Antibody against diphtheria, tetanus, pertussis (ELISA), hepatitis B (radioimmunoassay) and Hib polyribosylribitol phosphate (PRP) [radiolabeled antigen binding assay] was determined. Solicited local and systemic adverse events were evaluated on the day of each vaccination and for three subsequent days. Follow-up of unsolicited and serious adverse events was conducted for 30 days following each vaccination. Results: A total of 360 subjects were enrolled in the study. After completion of the three-dose vaccination course, seroprotective antibody concentrations against diphtheria, tetanus and hepatitis B, together with a pertussis vaccine response, were seen in almost all subjects with immunogenicity results (n = 336). All subjects had post-vaccination Hib anti-PRP antibody concentrations of at least 0.15 μg/mL, and 97.0% and 99.4%, respectively, of the subjects receiving a single or separate injections had Hib anti-PRP antibody concentrations ≥1.0 μg/mL. Addition of the Hib vaccine to the tetravalent DTaP-HBV vaccine did not increase the incidence of local or systemic reactions. Conclusions: Combination of DTaP-HBV and Hib vaccines in a single injection is safe, immunogenic and well tolerated, and thus has the potential to simplify the childhood immunisation schedule in Italy.