"A drug to dramatically cut the risk of HIV infection during sex would save the UK around £1bn over the next 80 years," reports BBC News. A modelling study looking at the cost-effectiveness of providing pre-exposure prophylaxis, or Prep, for men at risk of HIV, found it would reduce infections – and hence treatment costs – in the long term.
However, the costs of HIV treatment and prevention would rise for the first 20 years of providing the programme. Providing Prep would only save the NHS money after 30 to 40 years, depending on factors such as future costs of the drug.
Prep is a combination of two anti-HIV drugs, emtricitabine and tenofovir. Studies have shown that it is around 86% effective at protecting men who have unprotected sex with men from HIV infection. It can be used in two ways: daily, or on a sexual event basis – using it during periods of unprotected sex (for two days before, each day that unprotected sex takes place, and two days afterwards).
In the researchers’ model, a quarter of new infections of HIV among men who have sex with men would be avoided. Costs over 80 years would drop from £20.6 billion to £19.6 billion – a saving of £1 billion.
Prep is not routinely available on the NHS in England, although it is in Scotland. However, free HIV testing and post-sex prevention treatment are available from NHS sexual health clinics, and Prep is being trialled in selected clinics as part of a study.
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The study was carried out by researchers from University College London, the London School of Hygiene and Tropical Medicine, Public Health England and NAM (National AIDS Map) Publications.
BBC News gave a clear and balanced overview of the study.
This was a health economic evaluation done by a modelling study, using a model of HIV infection, behaviour and infection spread. Researchers wanted to see how HIV infections and costs would change over the next 80 years, with and without a programme to provide Prep to eligible men.
They wanted to know how much it would cost per quality-adjusted life-years gained (QALYs) – a standard measure for assessing cost-effectiveness.
Importantly, QALYs do not just measure total lifespan; they also take into account the quality of life.
Researchers used a simulation model called the HIV Synthesis Model, populated with figures from the UK. They looked at 22 variables and simulated outcomes with and without the introduction of a Prep programme. They looked to see what would happen to people's health, and to the costs of HIV, over an 80-year period starting in 2016.
Researchers made assumptions including:
They also tested their assumptions, looking at what would happen if Prep was not routinely used by men on the programme, or HIV testing increased, or sexual behaviour changed. They looked too at what might happen to costs of drugs used for HIV treatment and for Prep. Because these drugs are due to come off patent soon, they are likely to decline in cost, but we don't know how much costs will decline each year.
They carried out sensitivity analyses, to test the robustness of their results.
The researchers estimated that 44,300 HIV infections would be prevented over 80 years of a Prep programme – 42% of them by men taking Prep being directly protected from infection, and 58% of them by those men not passing on the virus to other partners. That's a drop of 25% in new infections, compared to the numbers expected without a Prep programme.
The cut in the number of HIV infections was likely to lead to a drop in the overall costs of HIV. The researchers said HIV would cost:
However, savings would not kick in immediately. Costs would be higher for between 30 and 40 years, because of the cost of providing the programme. For the first 20 years, in most scenarios, Prep would not be cost-effective. This is measured by the cut-off of £30,000 per quality-adjusted life gained, a commonly used health economist benchmark.
However, the figures depend a lot on drug costs. If the costs of anti-HIV drugs fell by 70% or more, the programme would be considered cost-effective after 20 years and save the NHS money within 30 years.
The researchers said their analysis showed that "the introduction of Prep in the proposed eligible population is cost saving". Indeed, they went so far as to tell BBC News that the introduction of Prep was "a no-brainer".
However, they admit in the paper, "commissioners will have to sustain an additional cost for the first 20 years, unless drug prices are substantially reduced".
Evidence to support the use of Prep is building. Studies have shown that it is very effective at reducing the chances of becoming infected with HIV, for men at risk of infection through unprotected sex with men.
The question is more about the cost of treatment – and who should fund it – than whether it works.
NHS England previously went to court to say that it should not be responsible for funding Prep, as it is a preventive treatment, and therefore should come under health promotion budgets held by local authorities.
The High Court ruled that the NHS was able to fund the drug. NHS England has since said it will begin making the drug available through selected sexual health clinics this autumn, as part of a 3-year trial.
Studies such as this provide important new evidence about the potential long-term costs and benefits of providing Prep. However, it's important to keep in mind that the study is based on modelling data using many different assumptions – which could turn out to be incorrect as the years go by. While Prep was cost-effective over the long term in all the sensitivity calculations done by the researchers, the time taken for it to become cost-effective varied widely, mainly depending on the cost of the drugs.
This study was limited to the effects of Prep on men who have sex with men, so we don't know whether the results would apply to women who have sex with men, or people at risk of HIV infection through drug use.
For information about HIV testing and how to protect yourself against HIV, see our information or contact your nearest sexual health clinic.