Gay men in New York rate an undetectable viral load as less effective than PrEP

Gay, bisexual and other men who have sex with men in New York City rate daily pre-exposure prophylaxis (PrEP) as the most effective HIV prevention strategy when condoms aren’t used, and considerably more effective than treatment as prevention or event-based PrEP, according to survey results published in AIDS and Behavior. Men rated these biomedical approaches far ahead of ‘strategic positioning’ or withdrawal before ejaculation.

The online survey was run between November 2016 and June 2017. While the city’s health department endorsed the “undetectable equals untransmittable” campaign in August 2016, widespread public discussion of U=U came later. In contrast, PrEP education and provision was already well established in New York at the time of the survey, no doubt influencing the results.

But while all HIV-positive participants were aware of treatment as prevention, few believed that it offered “complete protection”.


treatment as prevention (TasP)

A public health strategy involving the prompt provision of antiretroviral treatment in people with HIV in order to reduce their risk of transmitting the virus to others through sex.

strategic positioning

Another term for seropositioning.


In the context of drugs or alcohol, withdrawal is when a person cuts out, or cuts back, on using the substance, also known as detoxification or detox. In a context of sexual risk reduction, it refers to the insertive partner in penetrative sex withdrawing before ejaculation. It is not a particularly effective way to lower the risk of HIV transmission or pregnancy.


How well something works (in a research study). See also ‘effectiveness’.

event based

In relation to pre-exposure prophylaxis (PrEP), this dosing schedule involves taking PrEP just before and after having sex. It is an alternative to daily dosing that is only recommended for people having anal sex, not vaginal sex. A double dose of PrEP should be taken 2-24 hours before anticipated sex, and then, if sex happens, additional pills 24 hours and 48 hours after the double dose. In the event of sex on several days in a row, one pill should be taken each day until 48 hours after the last sexual intercourse.

The 732 participants were all men who have sex with men, living in New York City, recruited through advertisements on Facebook, gay websites and dating apps. As part of a broader survey on sexual health for men who have sex with men, they were asked:

“If an HIV-negative man and an HIV-positive man have anal sex together without condoms, how much protection would the following strategies provide against HIV transmission?” Five strategies were presented.

  • Daily PrEP: 70% believed this provided “a lot of” or “complete” protection. Current or former PrEP users were more likely to perceive this efficacy (86%) than other HIV-negative men (64%) or HIV-positive men (68%).
  • Treatment as prevention (defined as, “the HIV-positive man maintains an undetectable viral load”): 39% believed it offered “a lot of” or “complete” protection. Ratings were higher among HIV-positive men (58%) and PrEP users (49%) than other HIV-negative men (28%).
  • Intermittent PrEP (“the HIV-negative man takes PrEP/Truvada only soon before or after sex – like a day or two before and a day or two after”): 17% believed it offered protection.
  • Strategic positioning (“the HIV-negative man limits himself to the top position and the positive man to the bottom position”): 16% said this would give “a lot of” or “complete” protection.
  • Withdrawal (“if the HIV-positive man is the top, he makes sure to pull out before ejaculation”): 11% said this provided protection.

Whereas scientific studies now clearly show there is effectively no risk of HIV transmission from a sexual partner with a sustained undetectable viral load (a position publicly endorsed by the CDC and New York’s public health authorities), survey respondents showed some scepticism. Treatment as prevention was rated as providing “complete” (rather than “a lot of” protection) by 21% of HIV-positive respondents, 17% of PrEP users and 10% of other HIV-negative men. Similarly, only a minority of men believed daily PrEP offered complete protection.

Ratings for treatment as prevention did not vary by age, ethnicity, education, relationship status or number of sex partners, but men who identified as gay were more likely to believe it to be effective.

One in ten respondents (9.7%) did not know what PrEP was. Similarly, 6.1% did not know the meaning of an undetectable viral load. Whereas age, ethnicity and relationship status were not associated with lack of knowledge, it was more common in men without a college education (15.1% unaware of PrEP and 9.6% unaware of undetectable viral load) and men who identified as bisexual, heterosexual or other (26.0% and 11.6% respectively).

Not knowing these terms was rare in people living with HIV (2.3% and 0% respectively), but more common in HIV-negative men (11.3% and 7.5% respectively).

“Much still needs to be done to promote TasP [treatment as prevention] and make the strategy acceptable among MSM [men who have sex with men] and the general population,” the authors say. “Our findings confirm that TasP promotion needs to reach out to people who are not already engaged in HIV or PrEP care, and to MSM who do not identify as gay.”

Broadly similar findings were recently reported from an Australian study.


Siegel K & Meunier E. Awareness and Perceived Effectiveness of HIV Treatment as Prevention Among Men Who Have Sex with Men in New York City. AIDS & Behavior, online ahead of print, 29 January 2019. (Abstract).