National-level effectiveness of ART to prevent early mother to child transmission of HIV in Namibia

Background: Namibia introduced the prevention of mother to child HIV transmission (MTCT) program in 2002 and lifelong antiretroviral therapy (ART) for pregnant women (option B-plus) in 2013. We sought to quantify MTCT measured at 4-12 weeks post-delivery.

Methods: During Aug 2014-Feb 2015, we recruited a nationally representative sample of 1040 pairs of mother and infant aged 4-12 weeks at routine immunizations in 60 public health clinics using two stage sampling approach. Of these, 864 HIV exposed infants had DNA-PCR HIV test results available. We defined an HIV exposed infant if born to an HIV-positive mother with documented status or diagnosed at enrollment using rapid HIV tests. Dried Blood Spots samples from HIV exposed infants were tested for HIV. Interview data and laboratory results were collected on smartphones and uploaded to a central database. We measured MTCT prevalence at 4-12 weeks post-delivery and evaluated associations between infant HIV infection and maternal and infant characteristics including maternal treatment and infant prophylaxis. All statistical analyses accounted for the survey design.

Results: Based on the 864 HIV exposed infants with test results available, nationally weighted early MTCT measured at 4-12 weeks post-delivery was 1.74% (95% confidence interval (CI): 1.00%-3.01%). Overall, 62% of mothers started ART pre-conception, 33.6% during pregnancy, 1.2% post-delivery and 3.2% never received ART. Mothers who started ART before pregnancy and during pregnancy had low MTCT prevalence, 0.78% (95% CI: 0.31%-1.96%) and 0.98% (95% CI: 0.33%-2.91%), respectively.  MTCT rose to 4.13% (95% CI: 0.54%-25.68%) when the mother started ART after delivery and to 11.62% (95% CI: 4.07%-28.96%) when she never received ART. The lowest MTCT of 0.76% (95% CI: 0.36% - 1.61%) was achieved when mother received ART and ARV prophylaxis within 72hrs for infant and highest 22.32% (95%CI: 2.78% -74.25%) when neither mother nor infant received ARVs. After adjusting for mother’s age, maternal ART (Prevalence Ratio (PR)=0.10, 95% CI: 0.03 – 0.29) and infant ARV prophylaxis (PR=0.32, 95% CI: 0.10 – 0.998) remained strong predictors of HIV transmission.

Conclusion: As of 2015, Namibia achieved MTCT of 1.74%, measured at 4-12 weeks post-delivery. Women already on ART pre-conception had the lowest prevalence of MTCT emphasizing the importance of early HIV diagnosis and treatment initiation before pregnancy. Studies are needed to measure MTCT and maternal HIV seroconversion during breastfeeding.

Methods
We conducted a cross–sectional clinic-based survey assessing uptake of ART among HIV infected mothers and MTCT prevalence among their HIV exposed infants 4-12 weeks of age. We recruited caregivers (hereafter referred to as mothers) and their infants from those seeking routine immunization or postnatal care services in 60 selected public health facilities between August 2014 and February 2015.  We recruited caregivers (hereafter referred to as mothers) and their infants from those seeking routine immunization or postnatal care services in 60 selected public health facilities between August 2014 and February 2015.

We trained nurses at site level to identify all potentially eligible mother-infant pairs and work with trained data collectors to complete a standardized screening and interview questionnaire. For those who met the inclusion criteria, and provided written consent to participate in the study, we used the standardized questionnaire to gather sociodemographic data, clinical, treatment, and feeding data from the mother-infant pair. In addition to interviewing the mother, some clinical information was extracted from the maternal ANC cards and the infant child health passports (maternal HIV status, maternal ART use, infant HIV exposure status, and infant ARV prophylaxis).

Study nurses recorded infant HIV PCR tests and results in routine MOHSS clinic registers at each site. Confidential participant identification numbers were recorded in the study register(s) for infants/mothers enrolled in the study. The participant identification number was placed on the dried blood spot card, the laboratory request form, and the questionnaire. All interview data and laboratory results were collected on password protected smartphones and uploaded daily to a secure central database.