NEW YORK (Reuters Health) May 28 - Although the effectiveness of Haemophilus
influenzae type b (Hib) conjugate vaccine is reduced by more than half in
children infected with HIV, the vaccine's effectiveness in the overall
population is high enough to merit its use in developing countries where HIV
prevalence is high, according to results of a study conducted in Soweto, South
Africa.
Dr. Shabir A. Madhi and associates of the University of the Witwatersrand
in Johannesburg evaluated outcomes in infants vaccinated against Hib in 1998
as part of a phase III trial. Almost 20,000 children, for whom the prevalence
of HIV was estimated to be 6.03%, were vaccinated. The incidence of invasive
Hib disease until September 2000, was compared to that of approximately 22,000
children born in 1997 who did not receive Hib vaccination.
The estimated relative annual incidence rates in the unvaccinated, HIV-seronegative
children, was 170 per 100,000 children, Dr. Madhi's team reports in the April
issue of The Pediatric Infectious Disease Journal. The incidence rate was
nearly six times higher among the unvaccinated children who were HIV-positive.
In the children who received Hib conjugate vaccine, nine children
contracted invasive Hib disease, seven of whom were infected with HIV. These
results translate to a vaccine efficacy of 96.5% in the HIV-uninfected
children and of 43.9% in those with HIV disease. The overall Hib vaccine
effectiveness was 83%.
Dr. Madhi's team reports that three vaccinated HIV-infected children who
contracted Hib infections were evaluated for Hib IgG antibodies. Their titers
proved to be high enough that, under normal circumstances, they would have
exhibited short-term immunity. The researchers propose that these children's
antibodies were functionally impaired.
Therefore, the South African investigators recommend that clinicians
"perform functional antibody assays in HIV-1 infected children who are
recognized to have impaired cell-mediated and B lymphocyte activity."
Pediatr Infect Dis J 2002;21:315-321.
