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4. PrEP Use Widens, But Disparities Remain

Pre-exposure prophylaxis (PrEP) was again a major HIV story in 2016. The latest figures from a pharmacy survey by Gilead Sciences showed that more than 79,000 people in the U.S. have started Truvada (tenofovir/emtricitabine) for HIV prevention, but the survey does not include all PrEP providers and most experts think this estimate is low.

While PrEP use is now widespread in early-adopter cities like Chicago, New York, Seattle, and San Francisco -- where the Department of Pubic Health estimates that roughly 12,500 people may be taking PrEP -- it is not yet reaching everyone who might benefit.

Last year the Centers for Disease Control and Prevention (CDC) released a report indicating that more than 1.2 million people in the U.S. may be eligible for PrEP. Among the 44% of PrEP users with available race/ethnicity data in the Gilead survey, 74% were white, 12% were Hispanic, and 12% were black -- not reflecting the distribution of the HIV epidemic in the U.S., where 44% of new diagnoses occur among African-Americans. Studies show black gay men can achieve high levels of PrEP use and adherence if programs are tailored to their needs. Young gay men, too, can do well on PrEP but may benefit from extra support.

Outside the U.S., Truvada PrEP was approved in the European Union in August, but advocates and bureaucrats in the U.K. haggled over whether it is cost-effective and who should pay for it. Lack of PrEP availability in many countries has led people to seek generic tenofovir/emtricitabine from online sources or other countries, with a London study finding adequate drug levels and no evidence of counterfeits. Meanwhile, Australia is looking at an ambitious program to provide PrEP to gay men at high HIV risk.

A pair of rare cases of HIV infection while on Truvada PrEP were reported in Toronto and in New York City, in which gay men were infected with an uncommon multidrug resistant virus despite good adherence. Such cases remain rare, however, and experts and advocates continue to emphasize that PrEP is highly effective.

Looking beyond Truvada, researchers reported that the new tenofovir alafenamide (TAF) plus emtricitabine protects monkeys from infection with an HIV-like virus, but drug concentrations in human rectal and genital tissues may be too low. Gilead has embarked on a controversial trial comparing TAF to the older tenofovir disoproxil fumarate (TDF) for PrEP.

Long-acting injectable cabotegravir injections show promise for PrEP, though some people still have detectable drug levels long after the last dose -- dubbed the "long tail" problem. In December the National Institutes of Health and industry collaborators launched the large-scale HPTN 083 trial to test injectable cabotegravir administered every 8 weeks versus daily oral Truvada for gay men and transgender women. 

NEXT: 5. HIV Prevention for Women

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