HIV update - 10th June 2014

A round-up of the latest HIV news, for people living with HIV in the UK and beyond.

Transmission risks

Two weeks ago HIV update reported on an analysis which showed that even if the risk of HIV transmission during one sexual act is relatively small, the risk can accumulate over time for a couple who have sex regularly. The analysis suggested that effective HIV treatment provides more protection than condoms, but combining both strategies is safer. But when couples (where one person has HIV and the other doesn’t) have sex regularly for several years, the long-term risk may not be negligible.

Another analysis has been produced since then, also focusing on the risk of transmission when a person is taking effective anti-HIV treatment. Its findings are not exactly the same, but it also concludes that it is not possible for scientists to dismiss the transmission risk as zero.

While the two analyses have been done in different ways, both involve making calculations on the basis of previous studies. These are not new studies of new couples.

The most recent analysis was focused on the risks for a heterosexual couple, where one person has HIV and the other does not. The researchers pooled results from several previous studies examining transmission risks. In each study, the researchers had used genetic tests to prove that any new infections really did come from the main partner, not from someone outside the relationship.

They found four cases of HIV transmission in 1672 couples. Three of these infections occurred within the HIV-positive partner’s first six months on treatment and all four within a year. Full viral load suppression may not be achieved until six months after starting treatment.

The researchers calculated the risk of HIV being transmitted during a single sex act. They only considered sex that occurred when the HIV-positive partner had been taking effective treatment for at least six months.

They estimated the maximum risk to be 13 transmissions in every 100,000 sex acts. In other words, a risk of around 1 in 7700 for heterosexual couples. But they stress that these are the maximum figures – the actual figures could be lower, and might be as low as zero.

The uncertainty is because of the small number of couples who took part in previous studies and the limitations of statistics. There’s another, ongoing study which will be able to provide more definitive information when its final results are issued in 2017. And that study will include data on gay men as well as heterosexual couples.

Is it necessary to change treatment?

When HIV treatment does not work well and viral load is not undetectable, it is often recommended to change to new anti-HIV drugs. The raised viral load is usually a sign that the person has had difficulties taking their drugs on time. But a new study suggests that, in some cases, changing drugs may not be necessary.

This was an analysis of 209 people who were taking HIV treatment for the first time and whose drugs included a ritonavir-boosted protease inhibitor – either atazanavir (Reyataz) or lopinavir (Kaletra). Each person had ‘virological failure’ – in other words, their viral load had never fallen to an undetectable level, or it had been undetectable for a while but increased again later.

While viral load rising can often be a sign that the virus has developed resistance to one of the drugs being taken, this is not always the case. In general, protease inhibitors have fewer problems with resistance than drugs belonging to the non-nucleoside reverse transcriptase inhibitor (NNRTI, or ‘non-nuke’) class. In fact, very few people in this study had resistant virus.

One third of the people chose to switch to a new set of drugs, but two thirds chose to continue with their current drugs. Six months later, similar numbers in both groups (seven in ten people) had a low viral load, below 400 copies/ml.

People who said they had good adherence were more likely to have a low viral load.

The study didn’t use the most rigorous research methods (it’s not a randomised controlled trial). Nonetheless, the fact that the results didn’t differ according to whether people switched drugs or not suggests that in situations like these, switching drugs might not be necessary. The most important thing may be finding ways to improve adherence to treatment.

The findings won’t apply to people whose treatment doesn’t include a protease inhibitor, or to people who definitely have drug resistance.