Published: 16 April 2019

On-demand and injectable PrEP

By Heath Paynter, Deputy CEO, Australian Federation of AIDS Organisations (AFAO)

HIV pre-exposure prophylaxis (PrEP), the use of HIV medication by an HIV negative person to prevent HIV acquisition, has been enormously successful in protecting individuals who are at risk of HIV through sex. In New South Wales (NSW), Australia’s most populous state, HIV transmission among the most affected population group, gay and bisexual men, has fallen by thirty percent in 2018 compared to 2013. This success has been underscored by concentrated efforts from community-based organisations, historically operated by gay men, to mobilise demand for PrEP and by authorities to resource clinical and community operated healthcare clinics to rapidly respond to demand for PrEP. The outcome has seen PrEP use scaled up among gay and bisexual men in Australia. When the medication was listed on the Pharmaceutical Benefits Scheme (PBS) it was estimated that 17,000 people were using PrEP in Australia. Despite these successes, there are challenges to capitalising on the potential of PrEP to reduce HIV transmission.

For PrEP to be effective individuals need to take the medication as prescribed. Initially PrEP was recommended for daily use. As we have come to understand the science of PrEP’s effectiveness, other ways of using have been recommended, most notably, on-demand PrEP use. This is the use of two pills together, between two and twenty-four hours before sex, and then one pill every day until forty-eight hours has passed after the last time someone has sex. On-demand PrEP accommodates individuals who cannot use PrEP daily or express a preference for on-demand PrEP. For example, people who cannot tolerate daily use of PrEP because of an existing health condition, whose sexual practises are planned or individuals who cannot afford daily PrEP.

The focus of PrEP’s use in Australia has been for use by gay and bisexual men who engage in anal sex. PrEP is just as effective for people who are at risk of HIV through vaginal sex. On-demand PrEP does not provide high enough protection from HIV for people having vaginal sex and therefore is not recommended.

Even with the methods approved for use, it is critical that individuals inform themselves about PrEP and choose the best way to use it, in consultation with a doctor. These modes of using PrEP might become simpler very soon. A clinical human trial is testing the effectiveness of PrEP given through an injection every eight weeks. In effect, one injection of PrEP would provide eight weeks of protection from HIV, removing the need to take a tablet daily or on-demand. The trial is being undertaken among HIV negative gay and bisexual men and transgender women across the Americas, Asia and South Africa. The results of this trial are expected in 2021.