The spectacular failure of a large clinical trial of H.I.V.-prevention methods in Africa — and the elaborate deceptions employed by the women in it — have opened an ethical debate about how to run such studies in poor countries and have already changed the design of some that are now underway.
Scientists who conduct clinical trials are now testing participants’ blood more often and holding group discussions to quell rumors and urge participants to take their medications diligently.
As a result of the failed trial, scientists are arguing vigorously about the extent to which it is ethical to pay participants for their time, and whether results of trials that do so can be trusted.
The trial — known by the acronym Voice, for Vaginal and Oral Interventions to Control the Epidemic — was abruptly halted by independent safety monitors because it was not working: Women who were given pills or vaginal gels containing anti-H.I.V. drugs were becoming infected at roughly the same rate as women who were given placebos.
The study, paid for by the National Institutes of Health, was supposed to definitively establish whether pre-exposure prophylaxis — the use of small amounts of anti-AIDS drugs to prevent infection — would work for African women. It enrolled 5,029 women at 15 clinics in South Africa, Zimbabwe and Uganda, and cost $94 million.
In Africa, where there are 1.6 million new infections each year, women are at particularly high risk: About 60 percent of Africans living with H.I.V. are women, and teenage girls are far more likely to be infected than teenage boys.
The strategy has worked well for gay American men and Thai drug users who took their pills daily, but not for African women.
When parts of the trial had to be stopped prematurely in 2011, scientists suspected it was failing because some women were not using their gel or pills, even though they claimed they were and produced empty bottles and applicators to prove it.
But all blood samples had been stored for later testing, so the researchers had no idea how pervasive the problem was. The final analysis, published on Wednesday by The New England Journal of Medicine, said that about 70 percent of the women actually had no tenofovir, the main study drug, in their blood, even though about 90 percent had claimed they were taking their pills or using the gel, and counts of empty pill bottles and used gel applicators suggested that 86 percent had been taken or used.
Ariane van der Straten, a researcher who led follow-up interviews with over 300 participants, found that many admitted to discarding pills or pouring gel down the toilet.