Three-Dose Vaccination of Infants Under 8 Months of Age with a Conjugate Haemophilus Influenzae Type B Vaccine

Abstract

The first licensed Haemophilus influenzae type B (Hib) vaccines were of a purified capsular oligosaccharide. Unfortunately, oligosaccharides are poorly immunogenic in younger children and resulted in these vaccines not routinely being used until past the period of peak incidence of Hib disease. Subsequent Hib vaccine research revealed that conjugating the oligosaccharide with various carrier proteins could produce vaccines with varying degree of improved immunogenicity. We investigated the antibody response and side effects of HibTITTER, one such vaccine, in 96 young infants in our multi-ethnic, border population. A three-dose course was given concomitantly with DPT and OPV vaccines at 2, 4, and 6 months of age. Seventy-nine percent of the infants had obtained antibody levels reportedly associated with clinical immunity after the second vaccination and 96% after the third vaccination. There was no significant difference in response due to sex, race, or vaccine lot. Currently HibTITER is recommended for use at 18 months of age. Our data strongly suggest that it may be effectively used much earlier, thereby immunizing infants against Hib disease before they reach their age of greatest vulnerability.