The summary text explicitly called out why that would be unethical in this case.

They don't ask people to live their lives any differently than they would, nor do they expose anyone to HIV on purpose; they just track them assuming that x% of people get HIV in any given year. So they compare what X is for people who got the shot, vs those who did not.

As I skim TFA, they say nobody who got the shot ended up getting HIV, which would be statistical anomaly for the population they tested.

It's not "no shot," though. It's other existing, widely available forms of pre-exposure prophylaxis.

They're not comparing the new treatment to nothing. They're comparing it to existing treatments.

Oh, ok, I skimmed past this:

> The shot was also superior to once-daily Truvada, another Gilead drug that is used for HIV prevention.

That's good news. As I understand it the existing treatments were already very good. And these injections are only once per year.

Twice a year, but yes. That's a huge benefit -- not only is it easier for patients to stay on the treatment, but it's likely to be a lot cheaper as well.

I wonder how much variation there might be in terms of margin of error. Like, how close do they have to get to keeping people on a rigid 6-month schedule? Would 7 be fine? For what percentage of people? I'm assuming they have reason to believe once a year isn't enough, so that's an upper bound, but what's the lower one?

the short answer is no one knows (yet). if/once it gets approval, there likely would be a followup study on how much you can stretch the timing (possibly with dosage variation)

> I wonder how much variation there might be in terms of margin of error.

Probably quite a bit. The trial used the same dose of lenacapavir as what's used for maintenance in HIV patients; it's quite possible that less is needed to prevent infection in a healthy patient. Unfortunately, there's really no safe/ethical way for them to test lower doses.

It'll only be cheap once the patent expires. Until then, take those pills daily, y'all!