The Need for Condoms on PrEP, the HIV Prevention Pill

Questions raised after isolated infections are reported

Pre-exposure prophylaxis (PrEP) is a powerful tool for the prevention of HIV. PrEP traditionally involves the daily use of Truvada (emtricitabine/tenofovir alafenamide) or Descovy (emtricitabine/tenofovir disoproxil fumarate) to reduce the risk of getting HIV from sex by as much as 99%.

In 2021, a new injectable form of PrEP called Apretude (cabotegravir) was approved for use, protecting from HIV with just one shot every two months. Premarket studies suggest that people who take Apretude are 69% less likely to get HIV than even those who take Truvada.

With such effective preventive tools at our disposal, it may seem reasonable to ask if people need to worry about condoms if they are on PrEP,

A stack of condoms next to an open one
Rafe Swan / Cultura / Getty Images

This article takes an unbiased look at the real-world effectiveness of PrEP and some of the factors that may reduce its efficacy. It also explains the potential risks of ditching condoms and whether it's possible to get HIV even if you do take PrEP 100% as prescribed.

PrEP Usage in the United States

PrEP can work exceptionally well in preventing HIV, but it only works if you use it. And a lot of people aren't.

In 2020, just 25% of the 1.2 million Americans who could benefit from PrEP were taking it. Many were at high risk of infection, such as men who have sex with men (MSM) or couples in serodiscordant relationships (where one partner has HIV but the other does not).

Although many people qualified for PrEP are aware of its benefits, they often chose to avoid it due to concerns about cost, side effects, impact on insurance, or "not feeling at risk" of HIV. Others are perfectly happy to use condoms, and others express displeasure at the thought of having to take a pill every day.

Studies show that transgender women, who are at extremely high risk of HIV, are generally the less likely to know about PrEP and less likely to use it if they do (due to a general distrust of medical authority). This is concerning given that no less than 42% of transgender women in the United States have HIV.

Limitations of PrEP

PrEP is intended solely to protect people from getting HIV. It does not protect against any other sexually transmitted infection (STI). To this end, condoms—whether internal or external—still afford the best protection against most STIs.

Does PrEP Reduce Condom Usage?

When PrEP was first proposed as a preventive strategy, some public health professionals expressed concerns that it would encourage users to practice condomless safe (previously known as unprotected or unsafe sex).

Studies have shown that the opposite may be true.

Two different studies—the iPrEX OLE study conducted in the United States, South America, Thailand, and South Africa, and the U.S. PrEP Demonstration study involving MSM couples in New York and San Francisco—both reported that PrEP resulted in less condomless sex rather than more.

According to the PrEX OLE study, condomless receptive ("bottom") anal sex decreased from 34% to 25% after PrEP was started. Similarly, the U.S. PrEP Demonstration study reported a decrease in both the number of anal sex partners and the incidents of condomless anal sex.

This shouldn't suggest that PrEP will automatically reinforce safer sex practices in all at-risk groups. This is especially true in younger people, particularly younger MSM.

PrEP and Condoms in Young MSM

Younger people taking PrEP tend to have lower rates of treatment adherence and are more likely to engage in high-risk sexual activities than older people. On top of this, high rates of syphilis, gonorrhea, and chlamydia among younger people add to the likelihood of HIV infection, which may all but erase the benefits of PrEP.

A 2016 study from the Adolescent Medicines Trial Network (ATN) for HIV/AIDS Interventions reported that 90% of MSM aged 18 to 22 engaged in condomless anal sex while on PrEP and that the incidence increased the more adherent a person was to treatment.

The decline was rapid—from a high of 56% at week four to only 36% by week 48—during which time the rate of other sexually transmitted infections (22%) remained unchanged.

Can PrEP Fail?

PrEP has never been endorsed as a stand-alone strategy. Other means of protection are recommended, especially among people at high risk of HIV infection (including but not limited to MSM, transgender women, injecting drug users, and serodiscordant couples).

These concerns were amplified when four high-profile cases of PrEP failure were reported between 2017 and 2018. In each instance, the men were said to have been fully adherent to treatment based on the following circumstances:

  • The first case involved a 43-year-old MSM who took Truvada for PrEP for 24 months prior to testing positive. The man was thought to be adherent based on pharmacy records and the concentration of Truvada in his blood tests.
  • The second case involved an MSM in his 20s who was in a serodiscordant relationship. PrEP failure occurred four months after starting treatment. The testing of blood and hair samples confirmed that PrEP was, in fact, taken to what should have been optimal protective levels.
  • The third case involved a 34-year-old MSM who was on PrEP for more than a year before testing positive. Although he had not returned for HIV testing for more than a year, pharmacy records and blood and hair tests suggest that he was, in fact, adherent to treatment.
  • The fourth case involved a 50-year-old MSM who tested positive for HIV eight months after starting Truvada for PrEP. Lab results at six and eight months reported that Truvada levels in the blood were high, indicating a high level of adherence.

In three of the four cases, PrEP failure resulted in the transmission of a drug-resistant strain of HIV. For two of the cases, the HIV strain that they were infected with was multi-drug resistant.

What Is Transmitted Resistance?

Transmitted resistance is a situation in which a person with a drug-resistant HIV strain passes it to a partner. As a result, the partner will have "inherited" the resistance and will be less responsive to certain HIV drugs even though they have never been on treatment.

How Much Adherence Is Enough?

It can be safely assumed that higher rates of treatment adherence translate to higher rates of protection against HIV. After all, the CDC states that when taken as prescribed, PrEP can reduce the risk of getting HIV by around 99%. That's the general rule.

The problem is that it is not always clear how much PrEP adherence is "enough" to afford this level of protection.

On the one hand, a comprehensive study conducted in 2013 concluded that 80% adherence to oral PrEP (roughly six missed doses every month) equates to 100% effectiveness.

On the other, the IPERGAY study also conducted in 2013 found that the "on-demand" use of PrEP—in which two pills are taken two to 24 hours before sex and one pill is taken every 24 hours thereafter until sex is concluded—affords the nearly same level protection as daily PrEP. And this, despite the fact that only 43% of the participants took the drugs as prescribed.

While this strongly suggests that PrEP is pretty fool-proof, the results are not consistent, especially among at-risk females.

Research suggests that PrEP may offer less protection from HIV in females despite high levels of adherence. Compared to concentrations of Truvada in rectal tissues, the concentration of Truvada in vaginal tissues tends to be significantly—and sometimes impactfully—lower.

This disparity—paired with isolated cases of PrEP failure—illustrates that the risk of HIV, however low, is present.

The Verdict

Based on the available research, there is no clear-cut line between when PrEP provides near-perfect protection and not-so-perfect protection from HIV. As effective as PrEP can be, there is no way to responsibly say when condomless sex may be "safe."

Summary

Though HIV pre-exposure prophylaxis (PrEP) can reduce your risk of getting HIV by up to 99% if taken as prescribed, it is not perfect. There have been isolated cases where men who have sex with men (MSM) have gotten HIV despite evidence of optimal treatment adherence.

As such, there is no way to reliably say at what level of drug adherence or in which situations it may be "safe" not to use condoms.

A Word From Verywell

As effective as oral PrEP (Truvada and Descovy) may be in preventing HIV, the injectable drug Apretude may end up being the game-changer by ensuring stable drug concentrations in the blood for two months.

If you are having trouble taking oral PrEP as prescribed, speak with your healthcare provider about switching to Apretude, mainly if you are at high risk of getting HIV.

If you are in a serodiscordant relationship, it is equally essential for the partner with HIV to be on full-time antiretroviral therapy (ART). Studies show that by suppressing the virus to undetectable levels with ART, the risk of passing the virus to others can be reduced to zero.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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