PARIS, France (AFP) — “It’s magic,” said Francois, smiling. “Every time I take a pill I think about the people who aren’t so lucky as to have this option.”

Taking a drug normally prescribed to treat AIDS as a way to shield against the deadly disease — known as PrEP — is catching on, and proponents hope that it will soon have a measurable impact in reducing the number of infections.

“Besides its undeniable benefits for individuals, we need to know if PrEP confers a collective advantage too, with a lower number of new cases,” said French expert Jean-Michel Molina ahead of World Aids Day on Friday.

There are nearly 20 million people around the world taking anti retroviral therapy medication today, and another 17 million who need it.

HIV has infected 76 million people, and killed 35 million.

The idea behind PrEP — pre-exposure prophylaxis — is simple: High-risk individuals who are HIV-negative take Truvada, normally prescribed to patients already infected, in order to prevent the virus from taking hold.

Target groups are men who have sex with men, and heterosexual couples in which one person is HIV-positive. The World Health Organization has also recommended that sex workers adopt a PrEP regimen.

The United States, in 2012, and France three years later, were the first two countries to authorise this form of preventative treatment. Others have followed suit, including Canada, Kenya, Brazil, Thailand, Australia, Belgium, Scotland, and South Africa, where 19 per cent of the population live with HIV/AIDS.

In France — the first country in which PrEP has been made available without cost — “about five in 10,000 people” should be taking it, said Molina.

So far, there has been no measurable effect: In 2016, France saw 6,000 new infections, the same level as for the last 10 years.

“The number of people who have started PrEP — about 3,000 — is probably not enough to have had a statistical impact,” France’s public health watchdog agency concluded recently.

PrEP can be taken regularly [one pill a day], or “as needed” before and after sexual encounters. But treatment protocols must be scrupulously respected to ensure protection.

“We don’t yet have a vaccine against AIDS, but PrEP is a new and effective form of prevention, alongside condoms,” said Molina, who leads the ongoing Ipergay study for France’s AIDS research agency.

Francois, 55, is gay and lives in Paris. He has been on PrEP for 18 months.

“The sword hanging over my head has vanished,” he said in an interview.

“The day one forgets a condom or it breaks, I no longer have that sick feeling in the pit of my stomach.”

In France, “PrEPers”, as they are called, are required to have blood tests every three months, in part to scan for other sexually transmitted diseases not blocked by the treatment.

The European patent for Truvada, made by US firm Gilead, expired at the end of July, bringing generics onto the market. As a result, the average price of treatment has dropped from 500 to 180 euros (US$600 to US$210).