Men Who Took Daily Pill Stayed HIV-Free, Insurer Kaiser Permanente Says - San Francisco's largest private health insurer announced Wednesday that not one of its 657 clients taking a daily pill to prevent H.I.V infection had become infected over a period of more than two years.
That outcome opposed some critics' predictions that so-called pre-exposure prophylaxis, or PrEP, would lead to less condom use and more H.I.V. infections.
A study published in Clinical Infectious Diseases discovered that the people taking PrEP, almost all of whom were gay men, did use fewer condoms and fell victim to several other venereal diseases as a result. But none got H.I.V.
Dr. Jonathan E. Volk, an epidemiologist for the insurer, Kaiser Permanente of San Francisco, and the study?s lead author along with his team observed a large number of men involved in very risky behavior from mid-2012, when the Food and Drug Administration sanctioned the use of a two-drug combination called Truvada for prevention of H.I.V. infection, through February of this year. That sums to 388 "person years" of observation.
However, a clinical trial in 2014 among gay men in England found that participants who received a placebo instead of Truvada had nine infections for every 100 person years of observation, informed Dr. Anthony S. Fauci, the director of the National Institute for Allergy and Infectious Diseases.
All but four of the 657 participants in the Kaiser study were gay men, and 84 percent of them informed of multiple sexual partners. After starting PrEP, half of them got syphilis, gonorrhea or chlamydia within a year.
After the participants had used PrEP for six months, Dr. Volk's team observed 143 about their sexual behavior. More than 40 percent reported that their use of condoms had decreased. 74 percent, said that their number of sexual partners had remained the same.