HIV update - 18th July 2018

How effective are condoms during anal sex?

It is often assumed that condoms are close to 100% effective in preventing HIV transmission. This is the case during laboratory tests – where there is no scope for human error – but what about in real life?

Research shows that heterosexual couples who say they have used condoms consistently have around 80% fewer cases of HIV infection than couples who say they have not used condoms at all.

What about their efficacy when used by gay men for anal sex? An analysis published in 2015 found that gay men who said they used condoms all the time had 72% fewer HIV infections than men who never used them. This was for situations when an HIV-positive man is the insertive partner (‘top’) and an HIV-negative man the receptive partner (‘bottom’).

Now, a new study has come up with a considerably higher estimate of condoms’ efficacy for anal sex. These researchers say that condoms, used 100% of the time, stop 92% of infections where the HIV-negative partner is receptive.

Why is this new estimate so much higher than the previous one? One reason may be that the new researchers have more data to draw upon – they have pooled the data from four previously published studies, rather than two.

However, the crucial difference may be that they look at condom efficacy per number of partners instead of per sex act.

Counting the number of partners may be a more reliable guide to risk than counting sex acts. This is because in cases where a couple has sex many times, the risk tends to go down with time. HIV transmission seems to be more likely to occur during the first year of a relationship than later on. This may be due to variation in viral load – partners with high viral loads transmit in the first year, while those with low viral loads may never do.

Because there is less risk of infection as time goes on, the risk of not using condoms also diminishes over time – and so, therefore, does their apparent efficacy.

If on the other hand, someone continues having sex with multiple partners, their infection risk does not diminish over time because their chances of encountering someone with a high viral load stays constant – and therefore so does the efficacy of condoms.

For more information, read NAM's factsheet 'Condoms'.

Dolutegravir and resistance

Drug regimens containing the integrase inhibitor dolutegravir are durable and effective in people who have resistance to the older integrase inhibitors raltegravir and elvitegravir, according to Italian researchers.

The study involved 89 people who had taken a lot of different types of HIV treatment before. Each had previously taken raltegravir or elvitegravir, but their virus had developed resistance to it and the treatment had not worked.

After around one and a half years of follow-up, 89% were still taking dolutegravir and all of those still taking it had an undetectable viral load.

The ten individuals who had stopped dolutegravir did so after an average of three months of starting it. People with an HIV subtype other than B (the subtype that is most common in Europe) were more likely to need to switch.

But for most people, dolutegravir proved to be a durable and effective option.

For more information, read NAM's factsheet 'Dolutegravir'.

Drug-resistant TB

Drug-resistant tuberculosis (TB) is a major health problem in many parts of the world, including a number of African countries where people living with HIV are often affected. Multidrug-resistant tuberculosis (MDR-TB) is TB that does not respond to at least isoniazid and rifampicin, the two most powerful anti-TB drugs. Extensively drug-resistant tuberculosis (XDR-TB) is a form of multidrug-resistant TB with additional resistance to more anti-TB drugs that responds to even fewer available medicines.

Older treatments are only successful in around half of cases of MDR-TB and a third of cases of XDR-TB.

Since 2012 a new drug for treatment of drug-resistant TB, called bedaquiline, has been available. But with the notable exception of South Africa, many countries have been slow to use the new drug, partly because of some doubts about how safe and effective it is.

South African researchers have published data to show the benefit of using bedaquiline there. They looked at almost 20,000 people treated for drug-resistant TB, three-quarters of whom also had HIV. Overall, 13% of people treated with bedaquiline died compared to 25% of those who did not receive the drug.

After taking other factors into account, the authors calculated that for people with XDR-TB, treatment with bedaquiline was associated with an almost fourfold reduction in the risk of death. In people who had resistance to rifampicin or had MDR-TB, there was a threefold reduction in the risk of death.

The researchers say that bedaquiline should be used more widely.

For more information, read NAM's factsheet 'Tuberculosis'.

Vaccine research

Researchers trying to develop a vaccine for HIV prevention have announced some interesting results – and they may provide more details at the International AIDS Conference in Amsterdam next week.

People who don’t have HIV were given a series of injections, over a year. There were three differently formulated vaccines that were given in seven different permutations to groups of 50 volunteers each. An eighth group received placebo shots that didn’t contain any active ingredients.

The vaccine consisted of three components of HIV. Two were lengths of RNA from HIV’s genetic code, enclosed within the outer shell of two different viruses that help the vaccine get inside cells but don’t cause illness. The third was an HIV protein, gp140.

The aim was to induce a broad immune response. By various measures, this occurred in around four in five of the people taking it, with some of this maintained for up to a year.

A parallel study in monkeys found that the animals had a similar immune response. Moreover, the monkeys were ‘challenged’ with six rectal doses of a highly pathogenic Simian Immunodeficiency Virus that is similar to HIV. Two thirds of the monkeys remained free of infection.

It’s important to note that previous vaccine studies have had promising results in animals, but have not worked in humans. But these encouraging findings will renew interest in the large-scale trials of this type of vaccine that have begun in African countries.