Immunogenicity of a hexavalent combination vaccine in rhesus monkeys

Preclinical immunogenicity studies were conducted in rhesus monkeys to dete rmine whether there is immune interference in the response to one or more c omponents of a hexavalent vaccine (Hexavac(TM)) that contains antigens from Haemophilus influenzae (Hib), hepatitis B (HB), diphtheria (D), tetanus (T ), acellular pertussis (aP) and inactivated polio virus (IPV). Antibody res ponses were measured following co-administration of the components at three separate anatomical sites or administration as a hexavalent combination in a single site. After three injections of the hexavalent vaccine, the peak antibody responses to each component of the vaccine were > 100-fold above p re-immune titers and persisted at levels > 10-fold above pre-immune titers at approximate to1 year. Immune interference was observed in the peak respo nse to HE, D and pertussis toxin, but was not seen at later time points. Th e results indicate that the rhesus monkey model may be useful for pre-clini cal evaluation of combination vaccines. (C) 2000 Elsevier Science Ltd. All rights reserved.