Incidence and factors associated with mother to child transmission of HIV among exposed infants on HIV Prophylaxis in Tanzania from 2017 to 2021

Abstract

ABSTRACT Background: Roughly 160,000 children were newly infected with HIV in 2021 worldwide. Overall, 4% of people living with HIV (PLHIV) in 2021 were children aged 0 to <15 years. About 85% are from sub-Saharan Africa. In Tanzania, MTCT (Mother to Child Transmission) is 3.6% at six weeks and can triple by the end of breastfeeding if proper interventions are not taken. UNAIDS (Joint United Nations Program on HIV/AIDS) 2023 report states the overall transmission rate to be 6.9% including those who are breastfeeding. The provision of HIV triple therapy to HIV exposed infants is among the latest prevention opportunities. Despite these interventions, there is still a substantial rate of vertical transmission at 6.9% versus the country’s target which is <4% necessitating the need to assess the contributing factors especially after this latest intervention. Objective: The study mainly aims at determining the incidence rate of mother to child transmission and factors associated with transmission among HIV exposed infants receiving HIV prophylaxis in Tanzania. Methods: A retrospective cohort study involving mother-child pairs from all 26 regions of Tanzania’s mainland was conducted using existing routine data (secondary data) from the HIV care and treatment electronic (CTC3) database. All HIV-exposed infants aged ≤ 18 months registered in health facilities offering PMTCT services in the country from January 2017 to December 2021 were enrolled in the study. Infants were followed up for 18 months from birth; between June 2018 to June 2023. Data was summarized appropriately: Age was summarized by median and interquartile range after testing for normality. Categorical variables were summarized using frequencies and percentages. The incidence rate of MTCT is estimated. Factors associated with HIV transmission were established using a bivariable and multivariable Cox proportional hazard model. All analysis were considered statistically significant at 0.05 significance level. Results: A total of 16,917 mothers-infant pairs were analyzed, of which 8,578 (50.71%) were female infants. The overall incidence rate was 1.69 (95% CI, 1.63 – 1.75) per 1,000 person-years with variation across various groups (Antiretroviral drugs (ARV) adherence status and WHO clinical stage of the mothers, HIV prophylaxis provision at birth and feeding mode for the first six months of life for infants). Factors such as increase in age of the mother decreased the risk of vertical transmission. Infants born to mothers with poor ARV adherence aHR 2.52 (95% CI, 1.60-3.97), those who were mixed fed during the first six of months of life aHR 6.16(95% CI, 4.69-8.10) and those who were kept on Nevirapine therapy only aHR 3.89 (2.99-4.68) had elevated risk for mother to child transmission of HIV and the associations were statistically significant. Conclusion: Overall incidence rate of Mother to Child Transmission of HIV was found to be low after initiation of triple therapy prophylaxis for high-risk HIV exposed infants. However, the rate varies across various groups from mother factors to infant’s factors. Mother’s age, ARV adherence of the mother, feeding mode of the infant and type of prophylaxis given to the infant were identified as factors associated with mother to child transmission of HIV.