To try to amass data that could lead to the approval of condoms for anal sex, the company teamed up with researchers at Emory University, met with the F.D.A. and designed a study.
Funded by the National Institutes of Health, the study, the largest to date on condom effectiveness during anal sex, was conducted between May 2016 and May 2017. It involved 504 men, half of whom had sex with men and half of whom had sex with women, and the researchers took several steps designed to encourage more consistent and accurate data than previous studies, Dr. Siegler said.
After being trained in proper condom use, the men were given condoms and asked to fill out a daily diary on a phone app, to answer questions about whether they had had sex that day and whether the condom they used broke or slipped. The participants reported 2,351 anal and 2,533 vaginal sex acts during the study period.
Dr. Siegler said that the team had hypothesized that the condom failure rate during anal sex would be low enough to pass muster with the F.D.A., but had not expected it to be as low as it was — 0.7 percent — or that it would be lower than the failure rate during vaginal sex, which was 1.9 percent.
The researchers attribute the higher failure rate during vaginal sex to the fact that the study encouraged lubricant appropriate for condoms to be used for every instance of anal sex, but, adhering to public health guidelines, only encouraged lubricant to be used during vaginal sex “as needed or desired.”
So, while 98 percent of people who had anal sex used lubricant, only 42 percent of those who had vaginal sex did. When the researchers looked only at people who used lubricant, the failure rate in the vaginal group was 1.1 percent, making the odds of failure in each group essentially the same, the study reported.
Public health experts said that suggests that lubricant was critical to the study’s results, and in its statement, the F.D.A. said that during anal sex, the condom “should be used with a condom-compatible lubricant.”