Finlay Vaccine Institute is developing a new heptavalent conjugate vaccine against Streptococcus pneumoniae. As infants are the target population, PCV7-TT will be necessarily co-administered with other vaccines, and then, the interactions represent a concern. The aim of this work is to evaluate the possible immunological interferences in rabbits as animal experimental model. Rabbits were immunized with Heberpenta®-L, VA-MENGOC-BC®, and PCV7-TT. Blood samples were taken fourteen days after final immunization for obtaining sera. Antibody responses to all antigens were evaluated by indirect ELISA. Functional responses against diphtheria and tetanus toxoid were done by in vivo seroneutralization assay. No interference was observed by PCV7-TT over the humoral response against diphtheria toxoid and meningococcal antigens (p > 0.05). A nonstatistically significant reduction (p > 0.05) was observed in the case of the humoral response against Haemophilus influenzae type b oligosaccharide. Concomitant administration of Heberpenta®-L and PCV7-TT increased twice the antibody titers as well as the protective activity against tetanus toxoid, but no statistical differences were found. The co-administration did not induce a reduction in the percent of responders against pneumococcal polysaccharides contained in PCV7-TT vaccine. Concomitant administration of PCV7-TT did not induce interferences over the evaluated antigens of Heberpenta®-L and VA-MENGOC-BC®. Also, no interference was observed on the immune response elicited by PCV7-TT. These preclinical results suggest that PCV7-TT will not result in a serious problem over the immune response elicited by the licensed vaccines Heberpenta®-L and VA-MENGOC-BC®. However, the clinical interference could be strictly studied during clinical trials in infants.
Keywords: Concomitance; immune response; interference; nonclinical evaluation; pneumococcal vaccine.