No new HIV infections have occurred among nearly 5000 people who started Truvada for pre-exposure prophylaxis (PrEP) in the Kaiser Permanente Northern California health system, according to a letter in the 29 July edition of Clinical Infectious Diseases.

However, there were some infections in people who sought PrEP but decided not to take it or who started but then stopped, indicating missed opportunities for HIV prevention at various steps of the 'PrEP cascade'.

"Strategies are critically needed to ensure that patients start, restart or continue PrEP during periods of risk for HIV acquisition," the researchers concluded.

A growing body of research has demonstrated that daily or on-demand Truvada (tenofovir disoproxil fumarate/emtricitabine) is highly effective at preventing HIV when used consistently. Only three cases of PrEP failure have been reported under those circumstances (see report from CROI 2016, report from HIVR4P 2016 and report from CROI 2017).

Julia Marcus of Harvard Medical School and colleagues from the Kaiser Permanente Division of Research and Kaiser Permanente San Francisco Medical Center looked at the risk of PrEP failure defined more broadly, as occurring at any point along the continuum of care from the time a person first sought or was referred for PrEP through to ongoing consistent Truvada use.

This study included 7124 people who sought or were referred for PrEP at Kaiser Permanente Northern California from July 2012 through February 2017. Most were men who have sex with men. Read more via AIDSmap