whatever comes your way

Event-based PrEP offers flexible protection.



Six Easy Steps

Event-based PrEP (EBP) offers flexible protection against HIV, whether that’s for a single fuck, a dirty weekend, or fucking every day or two for a fortnight or longer.

With EBP the key is improvising within guidelines. You need to follow the guidelines, but also apply them to your own changing circumstances. As long as you keep doing EBP according to the guidelines, you’re protected.

This resource shows you the six easy steps to follow for flexible protection.

It has been designed for guys (including trans guys) who are thinking about using event-based PrEP (EBP) for HIV protection during anal sex. It provides plain language information to inform the conversations you may have with friends and partners – and doctors – about EBP.

This resource assumes you understand the basics of PrEP. If you’re not familiar with PrEP, we recommend starting here.

note for trans folk




In the 24 hours before your first fuck, take a startup dose of two pills.




Always leave at least two hours between taking a startup dose and fucking.

(You don’t need to do this with follow-up doses.)




24 hours after your startup dose, start taking one pill each day – around the time you took the startup dose.




Take a follow-up dose each day until two days after your last fuck.




If another fuck comes along less than 7 days after finishing up, you can restart by taking one pill instead of two. The lead-in, follow-up and finish-up rules apply as normal.




If you took a startup dose, but the fuck didn't go ahead and you didn't take a follow-up dose, do start-up again with two pills before your next fuck.


If you miss a dose or mess up the timing, talk to your doctor about your options. This may include starting PEP – see below for more details about risk.


About event-based PrEP

How do we know ebp works?

Studies show that EBP is just as effective as daily dosing.
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In 2010 we learned that taking a daily dose of an HIV medication can protect people from getting HIV through condomless sex. This is known as PrEP (pre-exposure prophylaxis). A study called iPrEx showed that PrEP works – as long as you take it as prescribed. A follow-up study found there were no HIV infections among participants who took at least four pills per week.

Some folks asked: what about only taking pills when you’re having sex? Another study called IPERGAY answered that question. Two hundred guys in France and Montréal took pills before and after sex. (We’ll show you the timing schedule below!) Known as ‘event-based’ dosing, this approach proved to be just as effective as daily dosing. Just like daily dosing, event-based dosing (EBD for short) only works when you take it.

As it happens, participants in the IPERGAY study were having a lot of sex. At least half were taking four pills or more per week – about the same amount that proved 100% effective with daily dosing. So the IPERGAY team also looked at data from folks having less ‘busy’ months, when they were using event-based PrEP less often. Result: EBP was still just as effective as daily dosing.
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Who should consider EBP?

The EBP approach involves thinking ahead, so it works best for people who can generally anticipate when sex is on the cards.
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You need to leave at least two hours’ lead-in before taking the startup dose and having sex – enough time for the pills to start working.

For example, if your sex life involves the occasional binge or blowout, like a sauna visit after work or a party weekend, or if you generally arrange hookups a couple of hours before meeting up, EBP may be an option for you to consider.

Other reasons for using EBP might include wanting to get more bang for your buck – reducing the overall cost of PrEP by only taking pills when you’re actually having sex. A small number of people experience continuing side effects during daily dosing, and using EBP might help you reduce the amount of time you experience those side effects.

If you are thinking of doing EBD, you also need to consider:

  • Do you normally have at least two hours lead-in before sex?
  • Are you generally pretty good at taking pills on time?
  • Can you handle the additional requirements of EBD?

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What kind of clinical care do I need?

You need all the same check-ups when doing event-based PrEP. Show more

When you start PrEP, you get tested for HIV and STI (sexually transmitted infections) and a kidney function test. It’s important to check that you don’t have HIV before you start PrEP, because the two drugs used for PrEP are not enough on their own to suppress HIV infection, and taking PrEP when you have HIV can limit some of your options for future treatment.

You also need follow-up STI checkups every three months, because PrEP only prevents HIV. Regular STI testing and treatment also help reduce the prevalence of STIs in the community. You should get vaccinated for hep A and HPV (if you are eligible), and it’s important to check that you don’t have hep B before using PrEP.

If you are thinking about, or have already started doing EBP, we recommend letting your doctor know so that they can support you. We have included key references and guidelines below, in case your doctor is not convinced about EBP. Show less

Making EBP work for you

Many of the resources for daily dosing list tips and strategies that work for EBP as well. Here are some recommendations for EBD in particular. If you find these ideas don’t work for you, go ahead and figure out what does — and remember to share what you learn with friends, your doctor and the PrEP community on Facebook.

set an alarm

When you take your startup dose, set a daily alarm on your phone at the same time of day. Label it something that will remind you to take your next dose. Turn the alarm off when you finish up.

use a pillbox

Buy a 7- or 14-day pillbox that you can carry with you. Each day you have a fuck, check there are pills in slots for another two days. (When you get to the last slot in the pillbox, just ‘wrap around’ to the starting slot.)

track your doses

You might like to try an app like Loop Habit Tracker (for Android) or Productive (for iOS). This allows you to track when you take your startup dose, the days you’ve fucked, and your follow-up doses, so you know when you can finish up (or restart). If apps aren’t really your thing, you could jot notes in a paper diary or calendar, or even on your arm.

plan ahead when partying

A party weekend — which could be a dance party or p’n’p — might change your usual routines for eating and sleeping.

Remember to take your pills to parties and play sessions. Bring a couple of extras in case you’re out longer than you expected.

If you take your startup dose late on Friday night, and by Monday you’re heading for an early night, take your follow-up dose before you go to bed.


Some people find that taking two pills at once is a challenge.

It is okay to take the two pills at different times, e.g. the first one at lunch and the next one at dinner.

Just make sure you leave two hours between the second pill and having sex – and take your first follow-up dose around 24 hours after the first pill.


Finding information and support

If you’re ever unsure how to proceed, ask for assistance right away!

  • Your doctor may be willing to provide contact details to answer brief questions.

  • Talk it over with friends to check your understanding of the way EBP works.

  • Your local AIDS council may have educators who can provide answers.

  • Ask a question in one of the many great Facebook groups for PrEP users (see links below).

  • You can find evidence on event-based PrEP written in plain language on sites like AIDSMap.

Clinical guidelines

The April 2018 update of the Australian clinical guidelines for PrEP includes new advice for clinicians on supporting patients to make an informed choice between daily dosing and ‘on-demand’ (event-based) PrEP. The relevant section is listed below (but check the guidelines for updates).

The choice of PrEP schedule: daily vs on-demand

PrEP can be used daily for long periods of time, and this is the most commonly prescribed PrEP regimen (also known as daily PrEP). PrEP can also be effective when used on demand, e.g. daily for short periods of time, or around single events of HIV exposure. The choice as to how to take PrEP should be made by the individual with advice from their PrEP provider.'

Daily PrEP

Daily PrEP should be recommended to people who have ongoing high or medium risk of acquiring HIV. In Australia, TDF/FTC has been registered for use as a daily medication.

On-demand PrEP

If exposure happens only for relatively short periods of time (e.g. during travel), or irregularly, on-demand PrEP can be recommended to cover the events of exposure and this strategy can be used on an ongoing basis. It may also suit those who have adverse events, such as nausea and diarrhoea, or changes in their kidney function, due to previous use of daily PrEP.

A word about PEP and risk

PEP is short for post-exposure prophylaxis, where you take anti-HIV medication daily for 28 days. You might consider PEP if you missed multiple doses on the EBP schedule.

U=U means Undetectable = Untransmittable, and it sums up the scientific evidence that shows a person with undetectable viral load poses zero risk of HIV transmission.

This is something to keep in mind in case you ever have to consider going on PEP.

The decision to start PEP is made on the basis of your risk exposure. U=U means that positive status does not mean ‘risky.’ Sex with partners with undetectable viral load is not a risk exposure.

The highest-possible risk is sex with a person in the first few weeks of HIV infection. They may not have any symptoms, and still believe they are HIV-negative, but their viral load is extremely high.

So if you’ve missed doses and you know your HIV-negative partners have missed doses – for example, running out of pills on a party weekend – talk to your doctor about starting PEP.

Resources and evidence

About this project

The project is an independent community initiative developed by Daniel Reeders, an experienced HIV campaign strategist, in partnership with Dr Darren Russell, an HIV and sexual health physician who has first-hand experience supporting patients using event-based PrEP in France. Our target audience is people who are considering or already using event-based PrEP – in marketing terms, the ‘innovator’ and ‘early adopter’ segments, who are willing to experiment, have a greater appetite for information, and who often become informal educators for friends, partners, clinicians and online communities.

The resource has been developed according to social marketing principles and the evidence on effective communication. The short film ‘Whatever comes your way’ takes a creative approach to illustrating how event-based dosing unfolds over time, and as a cultural product its frank language and cheeky visuals are intended to spark up a conversation around this neglected approach to PrEP.


We gratefully acknowledge an unrestricted educational grant from Dynamix International, with particular thanks to its founder Phil Joffe.

Executive producer 
Daniel Reeders (DNM Consulting and the Bad Blood blog)

Samuel Leighton-Dore (website and Facebook and Instagram)

Animator and sound design
Gisele Nour (website)

Graphic design and project manager
Lauren Austin (website)

Alex Fitch (NeedleDrop)

Nic Holas (The Institute of Many)

Clinical review was provided by Dr Darren Russell and Dr Trent Yarwood from Cairns Sexual Health Service. Materials and strategy were reviewed by Will Nutland (Prepster), Greg Owen (IWantPrEPNow), and Brent Allan. Special thanks to the many community members who provided feedback on the video and draft resource. Thanks to Ruth Sayers for production advice.