Antibody responses to haemophilus influenzae type b vaccines in men with human immunodeficiency virus infection

Background. Persons with human immunodeficiency virus (HIV) infection are at increased risk for serious infections caused by Haemophilus influenzae, yet there are few data on their antibody responses to the H. influenzae type b vaccines. Methods. We evaluated antibody responses in 248 men who were randomly assigned to receive a single dose of either the H. influenzae type b polysaccharide (PRP) vaccine or the polysaccharide—mutant diphtheria toxoid conjugate vaccine (PRP-CRM). The subjects were stratified into four groups: seronegative men (67 subjects), men with asymptomatic HIV infection (79), men with symptomatic HIV infection (47), and men with the acquired immunodeficiency syndrome (AIDS) (55). Results. Before immunization, the subjects with AIDS had the lowest PRP-antibody titers; 40 percent had titers below the putative protective level (<0.15 μg per milliliter). In the seronegative subjects, those with asymptomatic HIV infection, and those with symptomatic HIV infection, the PRP-CRM vaccine led to a threefold greater increase in geometric mean antibody titers than did the PRP vaccine (P<0.01). However, the subjects with AIDS had a greater antibody response to the PRP vaccine. The antibody response of HIV-seropositive men to the PRP-CRM vaccine correlated significantly with the number of CD4 lymphocytes (r = 0.47, P<0.0001, as compared with r = -0.01 for the PRP vaccine). In these HIV-infected men, both vaccines elicited the dominant anti-PRP idiotype described previously in populations not infected with HIV. Conclusions. Immunization with the PRP-CRM conjugate vaccine early in the course of HIV infection is likely to confer protection against disease caused by H. influenzae type b. (N Engl J Med 1991;325:1837–42.).