Safety and immunogenicity of a nonavalent pneumococcal vaccine conjugated to CRM₁₉₇ administered simultaneously but in a separate syringe with diphtheria, tetanus and pertussis vaccines in Gambian infants

Background. Unrelenting high morbidity and mortality have mandated that immunogenic vaccines be used to combat pneumococcal disease in infants. Objectives. To evaluate the safety and immunogenicity of a nonavalent pneumococcal conjugate vaccine and the antigenic interaction when administered simultaneously with diphtheria, tetanus and pertussis vaccines. Methods. Two hundred seven infants were randomized to receive three doses of either nonavalent protein conjugate pneumococcal vaccine (PnCV) or inactivated polio vaccine (IPV) at 2, 3 and 4 months of age with routine Expanded Program of Immunization vaccines as scheduled. Vaccinees were visited on Days 1, 2 and 7 to observe local and systemic adverse reactions. Blood was drawn before the first dose and 1 month after the third dose. Antibody concentrations in sera were measured by standardized enzyme-linked immunosorbent assay. Nasopharyngeal carriage of pneumococci was tested at 5 and 9 months of age. Results. No serious reactions were observed. Local induration and tenderness were observed more commonly at the site of administration of diphtheria, tetanus and pertussis vaccines than at the site of administration of IPV or PnCV. Between 79 and 91% achieved ≥1 μg/ml antibody against specific pneumococcal serotypes. Antibody responses to diphtheria and pertussis antigens were similar in both groups; however, antibody response to tetanus toxoid was significantly lower in infants who received PnCV (geometric mean concentration, 11.1 vs. 17.4; P < 0.001). Nasopharyngeal carriage in PnCV-vaccinated children was reduced but not significantly different from those vaccinated with IPV. Conclusion. Simultaneous administration of PnCV with Expanded Program of Immunization vaccines is safe and immunogenic. Immune response to the composite antigens is likely to confer protection.