Preventing HIV Transmission: How Effective Is PrEP?

Pre-exposure prophylaxis (otherwise known as PrEP) is an HIV-prevention strategy that uses antiviral medication to lower the chances of contracting the virus. It involves taking a pill every day, getting regularly tested for HIV and STIs, taking pregnancy tests and being monitored for kidney function.

The Food and Drug Administration​​ (FDA) approved PrEP in July 2012 after two clinical trials showed a reduction in the risk (by 42 percent and 75 percent) of acquiring HIV infection. As of today, health organizations such as the United States Centers for Disease Control (CDC) and the World Health Organization (WHO) only recommend the brand Truvada which is delivered orally. But given that it is a relatively recent advancement, many still have questions about the option of PrEP.

Who is it for?

PrEP is taken by HIV-negative individuals who may be at risk of being infected. These individuals include heterosexual men and women as well as homosexual men who engage in anal sex without condoms, serodiscordant couples, people who have had a sexually-transmitted infection (STI) within the past six months, and intravenous drug users who share needles.

It is dangerous for HIV-positive individuals to take PrEP as the virus may develop immunity against the medication. This is why regular testing is an essential part of the process. Those who have potentially been exposed to HIV can opt for PEP (post-exposure prophylaxis) within 72 hours after the exposure to prevent getting infected.

Is it 100% effective? Can it be used as a replacement for condoms?

Researchers state that PrEP is most effective when it is taken regularly as this ensures enough levels of the drug in the blood to be protective against HIV. However, it is not 100% effective. According to the CDC, consistent use of PrEP can lead to nearly 90% of a risk reduction. 

PrEP can only be prescribed by a health care provider and is not a replacement for condoms. It is intended to be used along with condoms and other risk reduction strategies to reduce the overall likelihood of being infected. In addition, it cannot protect against other STIs such as gonorrhea and chlamydia.

Is it safe? What are the potential side effects?

Studies have shown that PrEP is just as safe as taking aspirin and patients do not report any negative impact from the drug on their sex life. Side effects may not always occur and can vary from person to person. The most common ones include nausea, headaches, fatigue, and dizziness which are all short-term and typically disappear over the first few weeks. Rare cases have shown a slight decrease in bone density, though experts have stated that it is reversible

Patients who are just starting PrEP need to be on treatment for around 20-30 days before the drug can be considered effective. It is not advisable to begin engaging in high-risk sexual activities before the drug levels have stabilized in the blood.

It should also be noted that the PrEP pill need not necessarily be taken for life. Individuals may change their lifestyle (for instance, entering into a monogamous relationship with another HIV-negative person) when they may not be at risk of HIV anymore. Under these circumstances, with guidance from their doctor, PrEP can be stopped.