A man has tested positive to HIV at a Melbourne clinic while participating in a trial of PrEP, an antiretroviral drug credited with preventing the spread of the disease.
Subscribe now for unlimited access.
$0/
(min cost $0)
or signup to continue reading
This has sparked fears in the gay community about possible resistance to the medication - particularly after rumours about the strain circulated on social media over the weekend.
However, it is not yet known whether the man has contracted a drug-resistant strain, or if something else is to blame.
Pre-Exposure Prophylaxis (PrEP) is a medication taken daily by HIV negative people, and when taken every day PrEP has been shown to reduce HIV transmission by up to 99 per cent.
Globally, hundreds of thousands of people use PrEP and there have only ever been two confirmed cases of infection with a drug-resistant strain of the virus by someone taking the medication correctly.
Both of these were reported in 2016, one in Toronto and one in New York.
In Amsterdam earlier this year, there was a third case of PrEP failure in a man following the prescribed course, through transmission of a drug-sensitive HIV strain, however this is still being investigated.
There has never been a confirmed case of HIV resistant to PrEP in Australia.
It's understood just over a week ago, a male patient on the trial tested positive to HIV at a Melbourne clinic.
On Monday, a spokesman at The Alfred confirmed researchers were "reviewing the clinical details of a man who has tested positive to HIV while being a registered participant of the Victorian PrEPX study."
Another Melbourne man, who also uses the antiretroviral drug, said the case highlighted that there was still a risk with PrEP, even if it was small.
"This is not a silver bullet. It makes the risk real," the man, who has requested anonymity, said.
But he said would continue to use the medication because it remained "the most persistent way to combat HIV".
Doherty Institute director and infectious diseases physician, University of Melbourne professor Sharon Lewin said all people who start HIV treatment have a test for their own resistance to the drug before they begin the medication.
She said once researchers at The Alfred have determined whether the man had been correctly and consistently taking PrEP, the HIV virus itself will be analysed for resistance.
"In cases of someone testing HIV positive while taking PrEP, we would first take a detailed history to understand how PrEP is being taken and potential exposures," she said.
"We would then look at the genetic code of the virus as this can tell us whether it is a drug-resistant strain, or a non-resistant strain. We would also look quite closely at drug levels in blood and the immune response to the virus, when the anti-body test became positive."
About 3000 Victorians have enrolled in the PrEPX research study, which is examining how PrEP could reduce the rate of new HIV infections in Victoria.
Experts estimate 10 - 15 per cent of gay men in Sydney and Melbourne were using PrEP by the beginning of 2017.
There are up to 600 Victorians on the study's waiting list.
Professor Lewin said PrEP was extraordinarily effective and there was still an urgent need to expand access to PrEP nationally.
"We closely track circulating strains of drug resistant virus in the community," she said.
"On average 10 per cent of new diagnoses of HIV in Victoria are with a strain of virus that has evidence of drug resistance.
"I don't think there is any reason for alarm here. PrEP works and any rare cases of failure need to be investigated fully so we fully understand why this can very rarely happen."
PrEP is not yet listed on the Pharmaceutical Benefits Scheme, but will be considered in July.
A generic version of the antiretroviral drug, known by the name Truvada, costs about $1200 a month to buy in Australia, but can also be bought on the internet for less than $100.
