Giving gay men access to HIV-preventing PrEP medication would save the NHS up to £1bn over the next 80 years, according to experts.
A study by a team at University College London said that providing the drugs for men who have sex with men (MSM) should be a "no-brainer" for the NHS after predicting it could prevent one in four new HIV cases.
The research show that while PrEP would initially cost the NHS money, after 40 years the measure would become cost-effective as the falling number patients being treated on the NHS begins to be felt.
After 80 years, the drug would have delivered the UK a saving of £1bn, say the researchers.
"Not only is it a highly effective treatment, it will save money. It's a no-brainer so it's a good thing to do," Dr Alison Rodger, one of the study's researchers, told the BBC
Pre-Exposure Prophylaxis (PrEP) involves HIV-negative people taking an antiretroviral drug to avoid getting HIV.
Already available on the NHS in Scotland and in countries including the USA, France and Canada, studies have shown it to cut the risk of HIV infection by up to 86%.
After losing a costly court battle to avoid providing the drug last year, NHS England promised to funding a three-year trial of PrEP in 10,000 patients deemed most at risk from September, though due to delays it is yet to begin. PrEP is still not available routinely on the NHS.
Dr Michael Brady, Medical Director at Terrence Higgins Trust, said: "One of the key arguments against PrEP has been that it will cost the NHS too much money.
"This study firmly puts that claim to bed by demonstrating that, when appropriately targeted at those at risk of HIV, it is not only highly cost effective but, as the price of HIV drugs falls, will actually save the NHS money in the long run. Each HIV infection we prevent saves the NHS £360,000 of a lifetime of treatment and care.
"This cost effectiveness data underlines the importance of PrEP in the fight against HIV. It is not only highly clinically effective it is also cost effective."
As the debate about PrEP's availability rumbles on, Attitude's Editor-in-Chief Matt Cain recently began taking the drug to help dispel some of the myths surrounding the drug. Click here
to read his story.
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