Increasing access to Truvada (tenofovir/emtricitabine) as pre-exposure prophylaxis (PrEP) through online marketplaces appears to have at least partly contributed to a dramatic recent drop in HIV diagnoses at London’s largest sexual health clinic, aidsmap reports.

Known as Dean Street, the clinic diagnosed 626 new HIV infections between January and November 2015 and 373 new infections during the same period in 2016, a 40 percent drop. This dramatic, unprecedented decline occurred as HIV testing and sexually transmitted infection (STI) rates remained stable at the clinic, suggesting that decreased HIV testing and sexual risk taking did not play a significant role in the fall of the HIV diagnosis rate.

Researchers also do not believe that the HIV diagnosis rate fell because Dean Street began attracting people at lower risk of the virus.

In 2012, the clinic began pushing to treat HIV immediately in those who test positive for the virus. Because fully suppressive HIV treatment likely virtually eliminates the risk that people with HIV can transmit it to others, early treatment policies may help curb the spread of the virus in communities. However, this new policy did not lead to the kind of dramatic drop in new infections seen between 2015 and 2016.

In July 2016, the clinic improved its early-treatment protocol to provide same-day antiretrovirals (ARVs) to those diagnosed with HIV; 75 percent of those newly diagnosed now leave the clinic the day of their diagnoses with HIV treatment in hand. Because this shift in policy was so recent, however, researchers do not think it explains the clinic’s 2015 to 2016 drop in HIV diagnoses.

The recent change that is likely at least partially responsible for the drop in HIV diagnoses is the advent of the website, which instructs Britons on how to purchase inexpensive PrEP online. On October 19, 2015, the website referred its first user to the Dean Street clinic for the HIV testing and kidney monitoring that individuals would otherwise receive as a part of a standard, clinician-written PrEP prescription. A formal arrangement between the website and the clinic began in February 2016.

PrEP is still not readily available in the United Kingdom as it has been in the United States since July 2012.

Perhaps 350 to 500 people are now receiving PrEP monitoring at Dean Street while they obtain the HIV prevention tablets through the internet. Additionally, about 75 people who attend the clinic are still receiving PrEP through their participation in the PROUD study, which in 2015 showed that PrEP reduced the overall rate of the real-world study population by 86 percent.

Another London clinic, the Mortimer Market Centre, which is near Dean Street, also recently announced a major one-year drop in its HIV diagnosis figures—in its case, a greater than 50 percent decline. This clinic is also working closely with many people buying PrEP online.

To read the aidsmap article, click here.