Immunogenicity and Reactogenicity to Haemophilus influenzae Type b (Hib) Conjugate Vaccine Among Rural Alaska Adults

Background: Despite routine vaccination and declining disease rates, Haemophilusinfluenzae type b (Hib) invasive disease still occurs in rural Alaska. Colonization studiesindicate persistent transmission of Hib among village residents, including adults. As partof a project to eliminate Hib carriage in 3 rural villages, we evaluated a cohort of Alaskaadults for antibody response and reactogenicity to a single dose of Hib conjugate vaccine(HbOC).Methods: 75 previously unvaccinated, randomly-selected adults in one village received asingle dose of HbOC vaccine and completed a side-effects diary. Sera and oropharyngealspecimens were collected at baseline, 2 months and 1 year.Results: No participants were colonized with Hib or reported serious side-effects. Atbaseline, 97% of adults had IgG anti-PRP concentrations > 0.15 µg/mL, 69% >1 µg/mL,and 28% > 5 µg/mL. Two months post-vaccination, 100% of participants hadconcentrations > 0.15 µg/mL, 93% >1 µg/mL, and 86% >5 µg/mL. After 1 year, 98% hadIgG anti-PRP concentrations > 0.15 µg/mL, 86% > 1 µg/mL, and 67% >5 µg/mL. GMCswere 1.9, 33.3 and 8.4 µg/mL at baseline, 2 months and 1 year post-vaccine, respectively(p