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Comment by dhnajsjdnd | Hacker News Reader

I am curious how a trial for the HIV vaccine will proceed in a world where PrEP is available.

PrEP might be available, but there are still countries where it is not easily accessible, and where HIV is still spreading.

https://www.who.int/news-room/spotlight/why-the-hiv-epidemic...

I can see it going full steam ahead, myself, for a few reasons:

1) Do both, for additional safety.

2) PrEP has changed formulations, and may change again. This implies that the previous formulations were not completely optimal.

3) From what I understand, PrEP can be expensive, although your insurance may cover it. You can also get it overseas for much less but many are not comfortable with that.

4) It's a lifetime expense, even with insurance and a lifetime of having to take a drug versus one or more shots.

5) Not having to undergo kidney function tests on the regular might be nice.

The problem with “do both”: if you give your control group PrEP, then you won’t be able to get data to support the vaccine’s efficacy. A trial requires enough infections in the control group to show the vaccine is better.

That's only a problem for the studies. I'm talking about after the studies. I can see a lot of at-risk people saying "Yeah, I'll do both."

I was joking to my doctor that when I get access to the COVID vaccines, I plan on Moderna in one arm and Pfizer in the other.

The comment you replied to was specifically asking how the trial would work given PrEP though.

You pick a high risk group that either doesn’t have access to prep

For the HIV vaccine trials, all participants are educated about and are offered free PrEP. There will be participants who choose not to take the PrEP anyway, and there will be people who are not compliant with PrEP's dosing schedule, which will reduce its efficacy against HIV acquisition.

Drugs are controlled against the alternative treatment often enough. The study needs to be designed differently, but statistics can do this.

There's a lot of places in the world that have not approved PrEP. And just like a birth control pill, it has to be taken daily -- and that is something that is hard for a lot of people to do consistently.

Even in the West, isn't it really expensive?

The sticker price is very high but nobody pays it. It’s free even if you are uninsured, and if you are insured Gilead will reimburse you for any copay.

I think the production cost is not that much, so the high price is just a means of extracting profit from the insurance programs.

Unfortunately, you have to give Gilead massive amounts of PII and paystubs/etc for the uninsured free programme, which is utterly insane to an outsider to think about.

> It does not have to be taken daily. You can take PrEP 'event driven', it is 'approved' this way by the WHO for MSM: https://www.who.int/hiv/pub/prep/211/en/

(Apparently event driven PrEP is indeed not approved or recommended for women.)

> Even in the West, isn't it really expensive?

One datapoint: In Belgium the out of pocket cost is 5 euros per package of 30 pills.

I've looked into it and they offer free PrEP to anyone in the trials that wants to take it.

There are probably a lot of people who are willing to take a one-time vaccine but not an expensive, daily series of pills which aren't completely free of side effects.

The initial trials just need to establish that the vaccine is safe (no severe side effects) which could include those on PrEP and even those with no risk factor.

The larger, latter trial that needs to study efficacy could simply use a large population. While HIV transmission is much more rare outside of certain high risk groups, infection does occur through accidents or deviations in behavior (e.g an EMT gets a needle prick while trying to administer Narcan). It would take a larger population and longer study but it should still be able to reach statistical significance.

I didn't know about PrEP, but from what I've just read it has to be taken daily in order to be effective. A vaccine could be a safer method.

I agree it would be better in the end after it’s approved. I’m thinking about getting the ethics board to allow a trial where you have to give half of the participants a control (and the other half a possibly-ineffective vaccine), when a known-good alternative exists.

The other reply has a solid point. Maybe you can find a country where it’s not possible to distribute daily PrEP, but is possible to vaccinate people and then test them for HIV monthly.

True. On the other hand, the effectiveness of PrEP is thought to be as low as 74% among people who inject drugs. It might still be possible to find such people for trials. We should still see a statistically significant effect even if they are taking PrEP daily.

They solved the ethics problem by offering trial participants PrEP for free for the duration of the trials.

Some people who start the trial not taking PrEP will also continue the trial without taking the PrEP they're offered and educated about for free.

It does not have to be taken daily - https://www.iwantprepnow.co.uk/how-to-take-prep/

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