Condoms, 100% of the time: that was the HIV-prevention policy Adam MacLean, 36, observed with casual male partners ever since he came out in 1999. “We were taught in sex ed that sex equals death,” says MacLean, a lifestyle consultant in New York City, “because if you were gay you were going to get Aids and you were going to die. So condoms were absolutely required.”

But in 2016, after a five-year monogamous relationship came to an end, MacLean found that the rules had been upended.

In 2012, the US Food and Drug Administration approved the drug Truvada for use as HIV prevention, as “pre-exposure prophylaxis”, or PrEP. When HIV-negative men who have sex with men (MSM) take PrEP daily as prescribed, they lower their risk of contracting the virus by an estimated 99% or more.

At first, as men around him went on PrEP and often engaged in condomless sex, MacLean resisted. “And then all it took was one drunken night when I didn’t use a condom,” he said, to make him get his own Truvada prescription. MacLean’s condom use declined dramatically. So did his fear of HIV. But he may also have put himself at increased risk of contracting other sexually transmitted infections (STIs).

In the MSM community, a rapidly expanding STI epidemic is fueling questions about whether the steadily rising number of people who start Truvada for HIV prevention subsequently change their sexual behavior in ways that increase their risk of contracting chlamydia, gonorrhea, syphilis and, in rarer cases, hepatitis C.

‘Behavioral change’

In the US, public health officials are beginning to credit Truvada with pushing down HIV transmission rates. An estimated 180,000 Americans use PrEP, the vast majority of them MSM.

Worldwide, perhaps 100,000 more are taking it. In England, though the National Health Service has not backed the pill, many MSM are buying generic Truvada online. Australia has seen a recent dramatic increase in use, thanks in part to a study published in The Lancet HIV this month which found that putting thousands of men on Truvada was associated with a 25% one-year decline in HIV diagnoses among MSM in New South Wales.

In the first five years following PrEP’s US approval, most studies did not show convincing evidence that going on it was linked to significant sexual behavioral shifts, such as having more sexual partners, having sex more frequently or, as in MacLean’s case, using condoms less. Read more via the Guardian