Mucosal antibody response to parenteral vaccination with Haemophilus influenzae type b capsule

The simultaneous serum and mucosal antibody response to parenteral vaccination with the Haemophilus influenzae type b (Hib) polysaccharide capsule (PRP) was evaluated in a group of 10 children and nine adults. All subjects responded to parenteral vaccination with an increase in serum anticapsular antibody. The children's preimmunization anti-PRP antibody level (mean = 0.04 microgram/ml) and 3 wk postimmunization level (mean = 19.3 micrograms/ml) were lower than the adults' (preimmunization mean = 1.5 microgram/ml; postimmunization mean = 81.2 micrograms/ml). Eight of 10 children and seven of nine adults also developed a rise in antibody in nasal secretions. The children's mean nasal preimmunization level was 0.74 microgram/mg IgA and mean postimmunization level was 5.0 micrograms/mg IgA. The adults' mean nasal preimmunization level was 0.98 microgram/mg IgA and mean postimmunization level was 3.0 micrograms/mg IgA. Salivary antibody responses generally followed the pattern of nasal antibody responses. These data suggest that parenteral administration with the Hib capsular polysaccharide can produce a mucosal antibody response. Furthermore, although serum antibody responses to PRP vaccination are greater in adults than in children, mucosal antibody responses are comparable.