Brief introduction to PrEP

PrEP (pre-exposure prophylaxis) is taking two HIV medications (combined in one tablet) to protect against HIV infection. Of course, an existing HIV infection must be ruled out before PrEP is used; a detailed risk assessment and counseling is required, and HIV progress checks are performed every three months.

In Switzerland, PrEP has so far been used almost exclusively by men who have sex with men. A distinction is made between two types of intake*:

  • “Continuous PrEP” begins seven days before the first time you have sex without a condom and is taken daily during the period of unprotected sex and for another 7 days after the last unprotected sex, and only then is it stopped.
  • In “On-Demand PrEP,” two PrEP tablets are taken 2 to 24 hours before the first unprotected sex, then one tablet daily at the same time (+/– 2 hours), and one tablet each day for 2 days after the last unprotected sex.

New data on the use and safety of the “On-Demand-PrEP”

For the “On-Demand-PrEP” it says on “Although the data situation so far looks good, there are not yet as many studies for this intake scheme as for the permanent PrEP.”

It is good to speak such a word of caution. On the other hand, new data is constantly being added to the On-Demand PrEP. For example, updated data from the Prevenir study (France) and the Belgium national surveillance results (2017–18) were presented last week at the European AIDS Conference in Basel**. Observation of nearly 3000 PrEP users in France and about 2400 individuals in Belgium showed adherence as on-demand PrEP in nearly 50% in both countries. When performed correctly, no failure with newly acquired HIV infection was found with either continuous PrEP or On-Demand PrEP.

The final evaluation of both studies is still pending. Even if this information is just another building block of knowledge: They help to further consolidate the assessment of the “99% effectiveness*” of the On-Demand-PrEP as well.

*quote adapted from**

Lectures 11/8/19, PS11:

Dominique Costagliola, “PrEP persistence and associated factors: ananalysis from the ANRS Prevenir study.”
Jessica Deblonde, “Monitoring PrEP implementation in Belgium: nationalsurveillance results, 2017-2018.”