Archive | March, 2014

HIV prevention in the 21st century

15 Mar

A little over 700 HIV-positive men and women had sex with their HIV-negative partners 44 thousand times, without using condoms, and not a single new HIV infection was found! This result of a large European study was one of the big stories last week at the CROI meeting in Boston (Rodger, 2014, CROI). How this is possible? Well, the HIV-positive partners were taking modern antiretroviral drugs and they had almost no virus in their body that could be transmitted to their partners.

HIV drugs

In the last 30 years more than 20 different antiretrovirals were developed to treat HIV and thanks to those drugs HIV-positive people can now live long and healthy lives. The modern antiretrovirals are always taken as cocktails of multiple drugs, but nowadays these cocktails are often available as one-pill-per-day formulas and their side effects are really quite mild.

Treatment is also prevention

Until recently, most HIV-positive people waited quite a while before starting treatment. Guidelines suggested to wait until the immune system started to give up (as indicated by a CD4 count of less than 400). However, this is changing as it is becoming clear that treatment not only keeps the immune system of the HIV-positive person healthy, it also prevents transmission to his or her HIV-negative partners. A classic case of two birds with one stone!

More effective than condoms

It turns out that HIV treatment is much more effective in preventing transmission than condoms are. Of course, condoms work, when they are used. But people are much better at taking their HIV medication every night than they are at consistently using condoms. This shouldn’t come as a surprise. Many women take the birth control pill every night to prevent pregnancy. If everyone would use condoms all the time, the pill would be unnecessary for most women.

PrEP

For a long time, doctors hesitated to tell people that HIV treatment prevents transmission, because they were afraid that their patients would stop using condoms all together. The same fear plays a role with another use of antiretrovirals. Last year the FDA approved Truvada (a simple cocktail of just two antiretrovirals) for use by HIV-negative people to reduce their risk of infection. This is called “Pre-exposure prophylaxis”, or PrEP. PrEP works quite well. A large study amongst gay men in several different countries found that Truvada roughly halved the risk of infection (Grant, NEJM, 2010). Amongst the men who toke the pills 7 days a week, the risk was reduced by 99% (Anderson, Science Transl. Med., 2012)!

Truvada is a pill that consists of two antiretrovirals (tenofovir and emtricitabine) and is used for HIV prevention as well as HIV treatment (the latter case always in combination with a third drug).

Truvada is a pill that consists of two antiretrovirals (tenofovir and emtricitabine) and is used for HIV prevention as well as HIV treatment (the latter case always in combination with a third drug).

No drugs for healthy people?

99% efficacy, that sounds like a real breakthrough, doesn’t is? You’d think that gay men in San Francisco and other people at risk would start using Truvada en masse. However, this is not the case. The idea of HIV-negative people taking HIV drugs is very controversial (see this NYT article). First of all because doctors don’t like to prescribe drugs to healthy people. This is understandable, but I think that these same doctors wouldn’t hesitate to prescribe the birth-control pill to healthy women. Sometimes prevention is worth the side-effects.

Risk compensation

A second reason why PrEP is controversial is because of the fear of so called “risk compensation”, that is, the fear that people who take the pills feel safe and reduce their use of condoms so much , that in the end they are at higher risk of infection than without the pills. Regarding this point, there is some good news though: A recent paper (Marcus, PLoS One, 2013) showed that risk compensation did not occur amongst people in a large PrEP study, even amongst those who believed that the drugs were working very well to protect them against HIV infection. It seems to me that the time is ripe for large scale use of PrEP. Maybe one day, taking Truvada to prevent HIV becomes as normal as taking the birth control pill.

Even better

What would be really useful for many women in this world is a pill that combines HIV prevention and birth control in one! I hope someone is working on this.

Note: this blogpost is based on a column I wrote for Bionieuws, the newspaper of the Dutch Biology Institute.

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