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AIDS 2016: South Africa Has Driven Mother-to-Child HIV Transmission Down to 4%

Mother-to-child transmission (MTCT) of HIV at a population level was just over 4% at 18 months of follow-up in a national evaluation in South Africa, Ameena Goga, presenting on behalf of the South African prevention of mother-to-child transmission Evaluation Group, told participants at the 21st International AIDS Conference (AIDS 2016) this week in Durban. 

[Produced in collaboration with Aidsmap.com]

Although countries are working towards virtual elimination of mother-to-child transmission, and the numbers of infants born with HIV or infected post-partum have declined sharply since the introduction of combination antiretroviral therapy for mothers -- Option B and Option B+ -- the effectiveness of prevention of MTCT programs needs to be monitored in order to understand where infants are still becoming infected and what can be done to drive down transmission. Greater clarity about when infections are occurring after delivery can also help target interventions.

Data on national 18- to 24-month HIV-free survival -- the gold standard measurement of prevention of MTCT program effectiveness -- is very limited in resource-poor, high HIV prevalence settings. Goga cited just 4 studies undertaken since 2001.

Among 1797 (71%) HIV-exposed infants, cumulative mother-to-child transmission at 18 months was 4.3% (95% CI 3.7%-5%) as South Africa transitioned to Option B. 81% of MTCT and 67% of MTCT or death occurred within the first 6 months after birth, highlighting this critical time period for following HIV-exposed infants.

Among infants alive at 6 weeks and followed between 6 weeks and 18 months, HIV-free survival was 93.7% (95% CI 92.2%-94.8%).

From 2012 to 2014, Goga and her colleagues conducted a national evaluation to measure HIV MTCT and HIV-free survival. This was at a time when prevention of MTCT policy transitioned from Option A to Option B. The primary research question was among HIV-exposed infants, what is the national population level risk of MTCT, or combined MTCT or death, at 6 weeks, and 3, 6, 9, 12, 15, and 18 months?

A closed cohort of HIV-exposed infants was developed from a nationally representative cross-sectional survey conducted between 2012 and 2013 to estimate early (4 to 8 weeks postpartum) mother-to-child transmission. The findings are to be published shortly. To determine national estimates of 18-month HIV-free survival assuming a 5% MTCT rate and a 5% death rate, a target sample size of 1620 was needed.

The South African Prevention of Mother-to-Child Transmission Evaluation Group undertook 3 national surveys to measure national effectiveness: in 2010 when health policy provided maternal zidovudine (AZT) from 14 weeks of pregnancy, single dose nevirapine during labor, and infant nevirapine during breastfeeding (Option A); in 2011-2012 and in 2012-2013, during which time policy changed to triple antiretroviral therapy for all women living with HIV during pregnancy and breastfeeding (Option B). (Option B+, or ongoing ART for mothers, became policy in January 2015.)

A total of 580 facilities comprising public primary health clinics and community health clinics offering immunization services in all 9 provinces were randomly selected.

Infant dried blood spot specimens were taken at immunization visits at 4 to 8 weeks of age and tested for exposure to HIV, and if positive, tested for infection using total nucleic acid polymerase chain reaction.

In the 9120 infant dried blood spot specimens taken at 4 to 8 weeks of age, the national weighted infant HIV exposure prevalence and the national weighted risk of early mother-to-child transmission was 33.1% (95% CI 31.8%-34.4%) and 2.6% (95% CI 2.0%-3.2%), respectively. Early MTCT across provinces ranged from 1.5% to 5.4%.

All HIV-exposed infants, both antibody and maternal self-reported, were invited for facility-based follow-up at 3, 6, 9, 12, 15 and 18 months. Caregivers were interviewed and infants tested at each visit.

Of the target sample comprising 2811 eligible HIV-exposed infants, 6% mothers did not give follow-up consent. At each time point 1600 to 1700 infants were followed up. 71% (1797) of HIV-exposed infants were followed up at 18 months.

Cumulative MTCT by 3 and 6 months was 2.7% (95% CI 2.6%-12.6%) and 3.5% (95% CI 3.1%-4.4%), respectively. At 9, 12, and 15 months, cumulative MTCT was 3.7% (95% CI 3.2%-4.6%), 3.9%  (95% CI 3.4%-4.7%), and 4.1% (95% CI 3.5%-4.8%), respectively.

The cumulative MTCT rate at 18 months was 4.3% (95% CI 3.7%-5.0%). The most rapid increase in MTCT was seen within the first 6 months after birth, slowly increasing thereafter. Over 50% of postnatal transmission occurred by 6 months. Postnatal MTCT and intrauterine and early postnatal MTCT accounted for 39% and 61% of 18-month transmission, respectively. Similarly the most rapid increase in MTCT or death took place within the first 6 months.

Study limitations, Goga noted, included the exclusion of infants without consent or who died before 6 weeks of age and a closed cohort may underestimate MTCT and HIV-free survival. The strengths of the study, she concluded, lay in the nationally representative sample and the fact that 94.1% of the eligible population participated in the follow-up.

7/22/16

Reference

A Goga, D Jackson, C Lombard, et al. Highest risk of mother-to-child transmission of HIV or death in the first 6 months postpartum: results from 18 month follow-up of an HIV-exposed cohort, South Africa. 21st International AIDS Conference. Durban, July 18-22, 2016. Abstract TUAE0106.