Early post-partum viremia predicts long-term non-suppression of viral load in HIV-positive women on ART in Malawi: Implications for the elimination of infant transmission.

Background: Long-term viral load (VL) suppression among HIV-positive, reproductive-aged women on ART is key to eliminating mother-to-child transmission (MTCT) but few data exist from sub-Saharan Africa. We report trends in post-partum VL in Malawian women on ART and factors associated with detectable VL up to 24 months post-partum.

Methods: 1-6 months post-partum mothers, screened HIV-positive at outpatient clinics in Malawi, were enrolled (2014-2016) with their infants. At enrollment, 12- and 24-months post-partum socio-demographic and PMTCT indicators were collected. Venous samples were collected for determination of maternal VL (limit of detection 40 copies/ml). Results were returned to clinics for routine management.

Results: 596/1281 (46.5%) women were retained in the study to 24 months. Those retained were older (p<0.01), had higher parity (p = 0.03) and more likely to have undetectable VL at enrollment than those lost to follow-up (80.0% vs 70.2%, p<0.01). Of 590 women on ART (median 30.1 months; inter-quartile range 26.8-61.3), 442 (74.9%) with complete VL data at 3 visits were included in further analysis. Prevalence of detectable VL at 12 and 24 months was higher among women with detectable VL at enrollment than among those with undetectable VL (74 detectable VL results/66 women vs. 19/359; p<0.001). In multivariable analysis (adjusted for age, parity, education, partner disclosure, timing of ART start and self-reported adherence), detectable VL at 24 months was 9 times more likely among women with 1 prior detectable VL (aOR 9.0; 95%CI 3.5-23.0, p<0.001) and 226 times more likely for women with 2 prior detectable VLs (aOR 226.4; 95%CI 73.0-701.8, p<0.001).

Conclusions: Detectable virus early post-partum strongly increases risk of ongoing post-partum viremia. Due to high loss to follow-up, the true incidence of detectable VL over time is probably underestimated. These findings have implications for MTCT, as well as for the mothers, and call for intensified VL monitoring and targeted adherence support for women during pregnancy and post-partum.