Does U=U for breastfeeding mothers and infants? Breastfeeding by mothers on effective treatment for HIV infection in high-income settings

Can the campaign Undetectable=Untransmittable (U=U), established for the sexual transmission of HIV, be applied to the transmission of HIV through breastfeeding? European AIDS Clinical Society and, to some extent, American guidelines now state that mothers with HIV who wish to breastfeed should be supported, with increased clinical and virological monitoring. This Viewpoint summarises existing evidence on transmission of HIV through breastfeeding, differences in HIV dynamics and viral load between breastmilk and plasma, and the effects of antiretroviral therapy on infants. At present, insufficient evidence exists to make clear recommendations for the required frequency of clinical and virological monitoring for mother and infant in a breastfeeding relationship or for the action to be taken in the event of viral rebound. We propose a roadmap for collaborative research to provide the missing evidence required to enable mothers who wish to breastfeed to make a fully informed choice.