Immunity to six vaccine pathogens in HIV positive and HIV negative children in Equatorial Guinea.

Vaccination prevents millions of childhood deaths annually, yet 23 million infants still miss essential vaccines, mostly in Sub-Saharan Africa. Low coverage is particularly concerting in countries with high paediatric HIV prevalence. In Equatorial Guinea, where 6% of children live with HIV and vaccination coverage remains limited, information on vaccine-induced immunity is scarce. We conducted a cohort study to evaluate immunity against six vaccine-preventable diseases in HIV-exposed children from Bata. Plasma samples from 69 children (55 HIV+/14 exposed uninfected) collected between 2019 and 2021 were analysed by a chemiluminescent immunoassay. Despite antiretroviral therapy, only 18.5% of HIV + children achieved viral suppression. Reported vaccination coverage for DTP and measles was lower than WHO-UNICEF estimates. IgG antibody levels was 68.1% for diphtheria, 13% for tetanus, 5.8% for pertussis, and 49.3% for measles. Although mumps and rubella vaccines are not included in the national schedule, antibody prevalence was 79.7% and 59.4%, respectively, suggesting natural exposure. Vaccination records were incomplete for half of the children. HIV-exposed children in EG show insufficient antibody levels against major vaccine-preventable pathogens. Strengthening immunization services, improving vaccine record systems, and tailoring strategies for HIV-exposed children are critical priorities.