Low but detectable viral loads among women on antiretroviral treatment preventing PMTCT success in Malawi

20 June 2019

Women with low but detectable viremia account for one in six mother-to-child HIV transmissions among women on antiretroviral treatment.

mother and baby in Malawi

Although one of the first countries in sub-Saharan Africa to roll-out Option B+, where pregnant women are immediately provided antiretroviral treatment for life regardless of their CD4 count, little is known about how effective their treatment is for prevention of mother-to-child transmission of HIV (PMTCT) and the extent to which they are virally suppressed.

In Malawi, viral load monitoring is challenged by human resource shortages, difficulties in sample transportation to centralised laboratories, and laboratory capacity. There is also a lack of consensus as to when viral load monitoring should be carried out among pregnant and breastfeeding women, and the reality is that very few women have their viral load monitored.

Viral load ‘suppression’ is defined in Malawi and by the World Health Organization (WHO) as being below 1,000 copies/ml, but we know from evidence from South Africa that mother-to-child transmission has occurred in women enrolled in Option B+ with low-detectable levels of between 40 and 1,000 copies/ml.

In this cross-sectional study, investigators described rates of viral load suppression, factors associated with suppression and ratios of mother-to-child transmission, comparing rates of mother-to-child transmission among women with low-detectable, undetectable and unsuppressed viral loads at four to 26 weeks post-partum. 

Included in the final analysis were 1,274 mothers living with HIV and their infants, from the larger National Evaluation of the Malawi PMTCT Programme (NEMAPP) study between October 2014 and May 2016. All mother-infant pairs were followed up at 12 and 24 months. The study period occurred three years after the national implementation of Option B+ PMTCT guidelines in Malawi which provided lifelong ART (i.e. tenofovir/lamivudine/efavirenz).

Among women on ART, 34 transmissions occurred in total, with six (17.6%) among women with a low detectable viral load and 19 (55.9%) occurring among women with an unsuppressed viral load. Ratios of mother-to-child transmission were 0.9% for undetectable viral load, 7% for low detectable viral load and 14% for unsuppressed. Among women not on ART, rates were much higher at 14.3%, 21.4% and 30.3% respectively. 75% of the 32 infections occurred among women who learnt their status at the time of the study.

In a multivariate analysis, there was a nine-fold increase in the odds of HIV transmission when the mother had a low detectable viral load compared to when she was virally suppressed, and this increased to 17-fold when the mother was unsuppressed. 

The analysis found that suboptimal adherence was the strongest predictor of low-detectable viral load and being unsuppressed. The duration of time on ART, the mother being in adolescence and having lower levels of education were also associated with higher viral loads.

With 9% of the study participants having a low-detectable viral load (which accounted for one in six HIV infections occurring from women on ART), the authors noted: “These findings call for urgent discussion about the availability, timing and frequency of viral load monitoring in Malawi and whether viral load monitoring should be able to detect lower levels of viraemia (i.e. <40 or < 20 copies/ml).”

“Additionally, more research is required that explores optimal timing of viral load measurement and effective interventions for achieving viral load suppression in this population and the impact on eliminating paediatric HIV.”


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Written by Caitlin Mahon

Content Specialist - HIV & Sexual Health