FDA authorizes one-dose Covid-19 vaccine | Hacker News Reader

FDA authorizes one-dose Covid-19 vaccine

theverge.com

Once again, science saves the day!

Glad to see the FDA move quickly and prioritize things. Good work to all involved.

> FDA move quickly and prioritize things

Move quickly? Are you being sarcastic? What the heck is wrong with the FDA? They knew about this vaccine trial, everyone in the whole world knew. They were supposed to keep an eye on the trial and get data "live" and analyze it before J&J actually submitted for approval. Once they submitted, what took them so long? They are not running any experiments, they are simply reading a report. This is the third such report after Pfizer and Moderna. They have fresh experience with reading a report and coming up with all the possible challenges. It is their freaking job to understand p-values and significance levels. 1 month to read a report and say "yes, it looks good"? Are you kidding me?

Does anyone know why this vaccine "only requires one dose"?

Is the number of doses just an arbitrary decision by the manufacturers, or is it determined by the technology somehow?

One takeway from the Pfizer & Moderna trials was that a single dose of those vaccines were also fairly protective for most people. With those vaccines, if you could avoid being infected within two weeks of the first dose, it looks like the protection is ~ 90% against COVID. The second dose acts as a booster, and with J&J, a second dose does indeed increase the antibody titre about three fold. That said, a single dose of any of these vaccines is probably "good enough".

Couple of caveats: With Pfizer & Moderna, the major difference in outcome for single dose participants was a reduced protection from 'severe COVID', down to about 50%. It's also a very small group (~1000 people), so there's the risk of over interpreting the results.

The other thing to consider is that a second dose might be required for older adults, who have a reduced immune response from a single dose.

It's not arbitrary, but it's part of the design of the Phase 3 trial. One of the goals of the Phase 1 trial is to figure out the dosing, both the size and whether there is a booster needed and so on.

J&J has started a trial to evaluate adding a second dose. And of course there's lots of talk about delaying the 2nd doses of the other vaccines. It's likely enough they could have been approved as single dose vaccines. It'd be fascinating to have some insight into the conversations they had while deciding what dosing to trial.

> It's not arbitrary, but it's part of the design of the Phase 3 trial.

What I'm trying to understand is if there is any inherent difference that makes one vaccine suitable for one dose and another for two doses.

I still haven't seen anything answering this.

They try to work out the immune response in Phase I, and then use that protocol for II and III. I wrote the bit you quote because it gets determined before the efficacy trial. So it isn't arbitrary because they use data to work it out, and then it is sort of fixed once the later phases begin.

Given more money and so on they could probably do multiple simultaneous studies. With Covid, a trade-off there would be splitting up the enrollment and slowing down the results. 2 doses triggers a larger immune response, so it is one way to increase the likelihood that the studied dosing is found to be efficacious. And then they are also factoring in other understanding of the immune system, it won't just be about "more is better".

Oh, I see: You're saying they use data from Phase 1 to try to infer how many doses would be best.

That does make sense, but it must be pretty far from an "exact science".

To my (rather recent) understanding, all vaccines benefit from a booster dose. Because that's how the human immune system works.

Do you actually believe the number of doses would be an arbitrary decision? The effectiveness has been tested at different intervals after each dose. The manufacturing and logistics change dramatically when there is more than one dose. If one dose was needed the vaccinations could be mostly done in spring instead of through the summer.

I can't believe anyone would actually think something so crucial would be chosen arbitrarily or on a whim.

20 million US doses planned on delivery in March, 100 million "by June".

Very curious to see how states will choose to treat this with regards to eligibility. Open it up to a slightly younger cohort at lower risk? Treat it exactly the same as the mRNA vaccines?

I think between vaccinations that are complete and people not being sure about it, the criteria are going to be pretty broad by the end of April.

It is fascinating to watch younger internet people shoot for their appointments while not enough vaccine has been sent here to do first doses for the compiled waiting list of older folks.

My guess is that J&J with its easier logistics might end up being prioritized for rural & smaller communities. I doubt vaccine centers will have multiple vaccine types on hand to selectively give people based on an individualized risk assessment - you get what you get.

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