Why U=U does not apply to breastfeeding

Simon Collins, HIV i-Base

An excellent open-access review by Catriona Waitt from the University of Liverpool and colleagues in the Lancet HIV explains the differences between risks for sexual transmission and from breastfeeding, and proposes a roadmap for research.

This is important as the popular U=U campaign is specific to sexual transmission and is sometimes mistakenly interpreted as covering other transmission risks.

Most importantly, although breastfeeding is recommended by the WHO in settings when the benefits outweigh the risks of using formula milk, there are many reports of cases where HIV transmission from breastfeeding has occurred even when viral load is undetectable. These include when viral load is undetectable both in blood and breast milk.

There is currently no evidence that sexual transmission occurs when viral load is undetectable in blood.


Waitt C et al. Does U=U for breastfeeding mothers and infants? Breastfeeding by mothers on effective treatment for HIV infection in high-income settings. Lancet HIV. doi:10.1016/S2352-3018(18)30098-5(27 June 2018).

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