Background:
The WHO recommends considering infant postnatal prophylaxis (PNP) for breastfed HIV-exposed uninfected (HEU) children when their mother viral load (VL) is >1000 cp/mL. We aimed to assess the relevance of this threshold (derived from sexual transmission) by assessing whether mothers with a detectable VL below 1000 cp/mL were more likely to reach the 1000cp/mL threshold during the breastfeeding period.
Methods:
We pooled data from a phase 2 and a phase 3 clinical trials conducted in Burkina Faso and Zambia and evaluating similar preventive strategies. We recruited breastfed HEU infants and their mothers at 6-8 weeks (EPI visit 2) between 2019 and 2021. In the phase 2 trial and the intervention arm of the phase 3 trial, maternal VL was monitored by point of care (Xpert® HIV RNA) at 6-8W, M6 and M12 and the results were promptly given to mothers. Only HIV positive mothers with a VL < 1000 cp/mL at 6-8W postpartum and with available VL at M6 and/or M12 were selected for these analyses. The relative risk of having a VL >1000cp/ml at M6 or M12 was calculated in light of maternal VL at 6-8W.
Results:
Among the 679 selected mothers (140 from Burkina Faso and 539 from Zambia), 96 mothers had VL >40 copies/mL at 6-8W. Their median age was 30.9 years (IQR: 26.6-35.0), 73.6% of them were on antiretroviral treatment (ART) before this last pregnancy. During follow-up, 22(3.8%) and 19(19.8%) of women with VL < 40 and VL > 40 copies/mL at EPI-2 had one episode of VL >1000 cp/mL. Dolutegravir coverage increased from 29% at baseline to 87.3% at M12. Mothers with VL between 40 and 1000cp/mL at baseline were 5.2 [IC95%: 3.0-9.3] times more likely to have VL >1000cp/mL during follow-up than mothers with baseline VL < 40 cp/mL. Adjusting for maternal age, time to ART initiation, dolutegravir containing regimen at 6-8W, educational level, infant sex, country or parity did not modify the association between initial viral load measure and the subsequent risk of HIV VL > 1000 cp/mL.
Conclusions:
Mothers with viral load between 40 to 1000 cp/mL are at high risk of turning the 1000 threshold during breastfeeding, exposing their child to high risk of transmission while they are not considered for PNP. These findings challenge the ‘1000 cp/mL’ threshold for PNP initiation. Using the same threshold for PNP indication as the one for clinical HIV management could be programmatically simpler and could reduce the period at risk for HEU and therefore postnatal transmission.