I was deeply pleased by a recent report in The New England Journal of Medicine that demonstrated that mother-to-child transmission of HIV, accounting for more than 400,000 new infections per year, can now be eliminated. The study, carried out in Botswana, was led by my former colleague at Harvard Medical School, Max Essex. With no intervention, up to 15% of children born to HIV infected mothers are themselves infected. About one third of the infections occur in the womb, about one third at birth and a third through while breast feeding.
The Botswana studied showed that infection can be reduced to close to 1%, even for breast fed babies, if treatment with combination therapy for HIV of pregnant mothers begins six months into pregnancy and continues for an additional six months until weaning. Of the 709 babies born to this study, only 6 were infected in utero, and 2 during breast feeding. Untreated, 75-100 of the infants were likely to have been infected.
A second study also shows that it is possible to reduce infection during breast feeding. In this study, published in the same issue of The New England Journal of Medicine, mothers were treated with anti-viral drugs just before birth followed either by treatment of the mother with combination HIV therapy or of the child with a single drug for six months. Both regimes substantially reduced the risk of transmission during breast feeding.
This is very good news. Breast feeding avoids exposure to contaminated water and provides immunity critical to the survival of infants, especially in those parts of the world where HIV infection rates are highest.
Many of the women who participated in these studies did not receive continued treatment after weaning, as they did not meet current international treatment guidelines of having CD4 cell count of less than 200 or 350. I regard this as a mistake, as recent studies highlight the efficacy of continued treatment in both reducing the risk of disease and in reducing the risk of sexual transmission regardless of the CD4 cell count (see my earlier commentaries here and here).
I was played a significant role in the early efforts to reduce maternal transmission of HIV. As soon as the first drug, AZT, was shown to be effective as an anti-viral drug in people with AIDS, I suggested two additional uses for the drug. The first, treatment with AZT following HIV exposure to prevent infection, was rapidly adopted by health care workers following needle stick accidents.
The second idea was to use AZT to prevent mother to child transmission. This suggestion was met with great resistance. At the time WHO refused to initiate such studies. Even the physicians at Doctors Without Borders were doubtful. Many argued that the risks of treatment outweighed the possible benefits.
I decided that the only way to counter such skepticism was to prove the effectiveness in a primate model. SIV, the simian equivalent of HIV, is also transmitted from mother to offspring in Rhesus macaque monkeys. At the time, I was the Chief of the Division of Human Retrovirology at Harvard's DANA Farber Cancer Institute. I recruited Ruth Ruprecht, a retrovirolgist for this project. Working with Norman Letvin at the New England Primate Center, she demonstrated that AZT substantially reduced transmission of SIV from mother to newborn. The first human studies quickly followed. Over the years, treatment of pregnant women with AZT, and with the subsequent generations of anti-viral drugs that followed, have prevented infection of many thousands of newborns.
Now, some twenty years on, as the two recent studies show, we have both the knowledge and the tools to prevent HIV mother-to-child transmission altogether -- not just at birth but while breast feeding as well.