PrEP is the most effective HIV prevention tool we have
The reason that any instance of someone acquiring HIV while on PrEP is big news is because it’s so rare
We now have a pill that can prevent HIV. PrEP (pre-exposure prophylaxis) uses drugs that were developed to treat HIV to instead prevent someone from acquiring the virus. It has been heralded as the breakthrough drug that can bring an end to the HIV epidemic.
But how effective is PrEP?
Cases where someone on PrEP has acquired HIV have started to trickle in, spreading consternation among some users. Some have decided to stop taking the once-daily pill and revert to previous safer sex strategies. Other people who may have otherwise tried to get hold of PrEP have been discouraged.
The reason that any instance of someone acquiring HIV while on PrEP is big news is because it’s so rare. When someone who uses condoms acquires HIV it doesn’t make the news; it happens too often to be newsworthy.
Worldwide, more than 380,000 people have started taking the pill via official channels, almost two-thirds of them in the United States. It’s estimated that about the same number may have accessed PrEP via unofficial channels, particularly in China and Russia but also in the UK.
Out of all of these hundreds of thousands of PrEP users we have only a handful of reports of the drug failing, some of which have more clear evidence than others.
In 2016, there were two reports, one from Toronto and one from New York, of men who used PrEP consistently but became infected with uncommon HIV strains that were resistant to the drugs employed by the pill. Another two cases of drug-resistant PrEP were reported in 2018 from Seattle and San Francisco.
In 2017, researchers from Amsterdam reported the first case of a breakthrough infection that did not appear to be the result of drug resistance. The man concerned had an “unusually high number” of sexual partners – averaging 50-70 a month – and several other sexual infections.
Researchers have speculated he may have repeatedly exposed himself to HIV, which took a hold in his body after a slight dip in Truvada levels.
In other reported cases it has not been possible to verify that the individual had sufficient levels of the drug in their body to prevent infection (i.e. that they may have skipped too many doses for PrEP to be effective).
As a result of this handful of cases, some PrEP users are now worried that it is not effective and others, who are opposed to the pill for other reasons, have leapt upon these cases as proof that it doesn’t work. These reports confirm that PrEP doesn’t provide 100 percent protection against HIV but the more we learn about the pill, and the more we observe the impact it has on new HIV cases as its use increases, the more confident we become of its effectiveness.
PrEP as a strategy should be favourably compared with other safer-sex strategies.
Some people, who would say that their strategy is always to use condoms, don’t always use condoms. 100 percent condom use is rare. Even when condoms are used consistently, they can fail. With the low number of HIV cases among people actively taking PrEP we are now talking about greater than 99 percent effectiveness, in other words, the pill is more effective at preventing HIV than condoms.
It is vital to not let isolated cases obscure how effective the pill is. PrEP has played a significant role in bringing down new HIV infections in London, Sydney, New York, San Francisco and other cities around the world. Without PrEP there would now be thousands more living with the virus.
Sexual activity usually carries some risk, which is why we most often use the expression “safer sex” rather than “safe sex”.
PrEP may not always work – but for those who choose it, who are able to take it as directed, PrEP remains the most effective HIV prevention tool that we have.
Matthew Hodson is executive director of NAM aidsmap and the recent winner of Social CEO of the year. NAM aidsmap provides HIV news and treatment information to support people living with HIV, throughout the UK and internationally. @Matthew_Hodson
**We would like to thank Matthew Hodson for revisiting this early published work of his for publication on this website