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Fear of potential severe side effects may be the greatest barrier to long-acting injectable HIV prevention among men who have sex with men (MSM), followed by out-of-pocket costs, a researcher said.

When examining relative importance of perceived barriers to long-acting injectable pre-exposure prophylaxis (PrEP), perceived side effects was the most important, representing 52% of the total relative importance, reported Will Beckham, PhD, of Johns Hopkins University Bloomberg School of Public Health in Baltimore.

While out-of-pocket cost comprised 30% of the relative importance, other attributes were less important to this population, such as injection frequency (11%), stigma (5%), and service location (2%), according to data from an Internet survey of MSM presented at the virtual International AIDS Society Conference on HIV Science.

Results from the HPTN 083 trial presented in July 2020 found that long-acting injectable PrEP cabotegravir was superior to oral tenofovir/emtricitabine (TDF/FTC, or Truvada) for HIV prevention, but long-acting injectable PrEP has yet to be approved in the U.S.

The authors used the , a large annual survey of 10,000 cisgender MSM in the U.S. and territories. Participants were ages 15 and older, HIV-negative, and sexually active. Beckham's group then employed a discrete-choice experiment.

Beckham noted this methodology is commonly used to explore participants' preferences for a particular healthcare service or product. Participants are presented with a series of product features or attributes with varying levels, which allows researchers to examine all attributes relative to one another, unlike a traditional head-to-head comparison.

Participants were presented with two choices, each with varying levels of these attributes, and asked which they would prefer.

"Choice A, for example, might be mild side effects, injection done every 3 months, pay $25 out of pocket, injection done at a private doctor's office and a medium risk ... [of stigma] for being on PrEP," Beckham said.

Next to this, Beckham presented a Choice B, which was severe side effects, injection done every other month, $0 out of pocket, injection done at a pharmacy, and a low risk of stigma for being on PrEP. The data was based on how participants respond to different combinations with different levels of options.

Following a question about how likely they would be to use long-acting injectable PrEP, those who answered "very unlikely" were removed, leaving 2,241 MSM. A little less than two-thirds were younger than age 30, 63% were white, 78% had some college education, and 60% were urban/suburban. In the past 12 months, 84% reported having two or more male partners and 73% reported condomless anal sex. About three-quarters of MSM said they would be willing to use oral PrEP and 28% said they were using it currently.

Avoiding side effects was by far the most important barrier to use. Based on the responses, Beckham's group estimated that respondents would be willing to pay $84 for a "one unit change" in severe side effects, which were defined as needing to seek professional healthcare services to treat them.

Beckham encouraged implementing effective social and behavioral strategies to potentially encourage PrEP usage and effective communication of clinical data.

"Fear of side effects is going to be strong whether or not they reflect the reality of what the injection actually entails. We will have to address those fears and ... perceptions" if we want people to use injectables, he said.

Beckham also emphasized the importance of out-of-pocket cost, which would be particularly relevant for youth, racial, and ethnic minorities, as well as those of lower socioeconomic status. Increased insurance coverage and other subsidies would help with these barriers, he noted.

Session moderator Dulce Ferraz, PhD, of Fundação Oswaldo Cruz in Rio de Janeiro, said she was surprised that more respondents weren't concerned about stigma. Beckham responded that may be due to the "changing landscape" of stigma in the U.S., where PrEP is now perceived more as "a good thing for gay men to do to protect themselves and others."

He also added that privacy might be a factor.

"Because it is injectable, it's easy to hide, so instead of having that daily pill at home that a partner might see in your medicine cabinet ... it's something you can sneak away to the clinic, get it, and forget it," Beckham said.

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