Half of HIV-positive gay men disagree that HIV treatment makes you less infectious

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A survey of over 2000 gay men attending clinics in the UK has found that 48% disagree that HIV treatment can make someone less infectious or makes it unnecessary to use a condom, the eleventh International Congress on Drug Therapy in HIV Infection in Glasgow heard this week.

Although the ASTRA (Antiretrovirals, Sexual Transmission Risk and Attitudes) survey found that only 15% of men had recently had unprotected sex with someone of negative or unknown HIV status (serodiscordant unprotected anal intercourse or sdUAI), it discovered that that the minority of men who were not taking antiretroviral therapy (ART) were actually rather more, rather than less, likely to have unprotected sex with a partner of negative or unknown HIV status than men taking ART.

However, in gay men who were taking ART, those with a detectable viral load were considerably less likely to have sdUAI than men with an undetectable viral load, suggesting some men are taking their viral load into account when making decisions about unprotected sex.


detectable viral load

When viral load is detectable, this indicates that HIV is replicating in the body. If the person is taking HIV treatment but their viral load is detectable, the treatment is not working properly. There may still be a risk of HIV transmission to sexual partners.


A serodiscordant couple is one in which one partner has HIV and the other has not. Many people dislike this word as it implies disagreement or conflict. Alternative terms include mixed status, magnetic or serodifferent.

unprotected anal intercourse (UAI)

In relation to sex, a term previously used to describe sex without condoms. However, we now know that protection from HIV can be achieved by taking PrEP or the HIV-positive partner having an undetectable viral load, without condoms being required. The term has fallen out of favour due to its ambiguity.

statistical significance

Statistical tests are used to judge whether the results of a study could be due to chance and would not be confirmed if the study was repeated. If result is probably not due to chance, the results are ‘statistically significant’. 


The result of a statistical test which tells us whether the results of a study are likely to be due to chance and would not be confirmed if the study was repeated. All p-values are between 0 and 1; the most reliable studies have p-values very close to 0. A p-value of 0.001 means that there is a 1 in 1000 probability that the results are due to chance and do not reflect a real difference. A p-value of 0.05 means there is a 1 in 20 probability that the results are due to chance. When a p-value is 0.05 or below, the result is considered to be ‘statistically significant’. Confidence intervals give similar information to p-values but are easier to interpret. 

The survey also found that beliefs about viral load and infectiousness did have an influence on safer-sex decisions, with men who did not believe that viral load reduces infectiousness being less than half as likely to have sdUAI as men who believed that it did.

Study details

For this study, questions answered by 2086 men out of over 3000 answered in the last year were analysed. Their average age was 43, 88% were white and 85% were on ART. Of these 83% had an undetectable viral load, so over 70% of the whole group had an undetectable viral load on treatment. Just over 8% of men knew they had a detectable viral load and the same proportion did not know their viral load.

The men were asked whether they agreed with two statements: “When a viral load is undetectable, condoms are not needed to prevent HIV transmission” and “Undetectable viral load makes someone less infectious to a sexual partner”. Only 4% agreed with the first statement; 48% agreed with the second, leaving another 48% who agreed with neither.

Just under two-thirds of the men (64%) had had any anal intercourse in the last three months, and 37% had had any unprotected sex, but over half of these only had unprotected sex with another positive partner or partners. This means that 15% had sdUAI: of these 40% only took the receptive role when they had unprotected sex, indicating some ‘seropositioning’ behaviour, while 20% only had sdUAI with one regular partner.

Serodiscordant UAI was actually rather more common in men who were not on ART: 20% (3% of the whole group) were not on ART but had sdUAI, while 14% of men on ART (12% of the whole group) had sdUAI. Thus men off ART were 25% more likely to have sdUAI then men on it, and this was statistically significant (p=0.006). However, only 9.4% of men who were on ART but did not have an undetectable viral load had sdUAI, so if men were on ART, they were 40% less likely to have sdUAI than if they were detectable.

One reason men not taking ART might have more unprotected sex is because sdUAI was high in men who had only recently been diagnosed: 23% of men diagnosed within the last three months had sdUAI, but more than three months after diagnosis this had reverted to 14%. Young people (who might be more recently diagnosed and less likely to be on ART) were also more likely to have sdUAI: 24% did so.

Other factors associated with sdUAI were recreational drug use, which more than doubled the likelihood of sdUAI, and alcohol, which increased it by 50%; men with hepatitis C were also 50% more likely to have sdUAI, though this may be effect rather than cause. Ethnicity, employment, education, smoking and CD4 count were not associated with sdUAI and importantly, in this study at least, depression was not associated with it.

The chance of having sdUAI increased with the number of partners men had. While 39% of men had not sex in the last year, one in eight had had more than 20 partners and 4.4% more than 50. Amongst these latter groups, respectively a third and nearly a half had had sdUAI in the last three months.

These findings obviously have, as the researchers comment, implications for prevention strategies in the UK, particularly in terms of the complex question of whether making people aware of the benefits of treatment as prevention may have the effect of increasing risk behaviour.


Lampe F et al. ART use, viral suppression and sexual behaviour among HIV-diagnosed MSM in the UK: results from the antiretrovirals, sexual transmission risk and attitudes (ASTRA) study. Eleventh International Congress on Drug Therapy in HIV Infection, Glasgow, abstract O323, 2012. View abstract here.