HIV-1 infection as a risk factor for incomplete childhood immunization in Zambia

Immunizations are of particular importance for human immunodeficiency virus type 1(HIV-1)-infected children as they are at increased risk of severe disease and death from several vaccine-preventable diseases. Outside the United States, however, research on the impact of the HIV-1 epidemic on childhood immunization coverage is sparse. We conducted a nested case-control study in hospitalized children with measles to assess whether HIV-1 infection was a risk factor for incomplete immunization with diphtheria-tetanus-pertussis vaccine (DTP) and oral polio vaccine (OPV). Of 473 children, whose immunization status was determined from the immunization record or maternal recall, 23% were incompletely immunized and 19% were HIV-1 infected. After adjusting for age, sex, and measles vaccination status, HIV-1 infection was significantly associated with incomplete immunization with DTP and OPV (adjusted OR 1.9; 95% CI 1.1, 3.3). In a subset of children for whom information on maternal education was available, less than 7 years of school education was a risk factor for incomplete immunization (adjusted OR 3.7; 95% CI 1.8. 7.5). Children from homes with more than three children were twice as likely to be incompletely immunized as those from homes with one to three children. Our findings suggest that HIV-1-infected children are at increased risk of vaccine-preventable diseases not only because of impaired immune responses but because of lower rates of vaccine coverage.