PERSISTENCE OF ANTIBODY-RESPONSES TO HAEMOPHILUS-INFLUENZAE TYPE-B POLYSACCHARIDE CONJUGATE VACCINE IN CHILDREN WITH VERTICALLY ACQUIRED HUMAN-IMMUNODEFICIENCY-VIRUS INFECTION

Background. Recurrent bacterial sepsis is common in pediatric HN infec tion and immunization against Haemophilus influenzae type b (Hib) is r ecommended. Long term persistence of anti-Hib antibody and the need fo r, or timing of, a booster dose has not been adequately studied. Metho ds. Immunogenicity during a 12-month period following immunization wit h Hib-tetanus conjugate vaccine (ACT-HIB(R); Merieux) was evaluated in 48 vertically HIV-infected children and 36 uninfected children, born to HIV-positive mothers. A titer of anti-Dib polysaccharide antibody o f greater than or equal to 0.15 mu g/ml was considered to indicate sho rt term and greater than or equal to 1 mu g/ml long term protection. R esults. At 1 month postvaccination 36 (100%) uninfected and 42 (88%) H IV-infected children achieved titers of greater than or equal to 1 mu g/ml. However, by 1 year titers had dropped below this value in 18 (43 %) infected compared with only 4 (11%) uninfected children (chi square , 9.7; P = 0.002). Although the rate of fall of antibody titer was gre ater in uninfected than in infected children, this was no longer the c ase after adjustment for the 1-month postimmunization titer. The rate of antibody titer decline was not significantly related to HIV disease status or to either the age-related CD4 count at the time of immuniza tion or the change in age-adjusted CD4 count during the 12 months afte r immunization. Conclusions. Not only was the initial antibody respons e to Hib conjugate vaccine decreased in children with HIV infection an d AIDS but also 1 year later only 57% of the initial responders had pe rsisting titers above the level associated with long term protection. The need for reimmunization of children with HIV infection against Hib requires further evaluation.