Second dose important for overall durable immunity in animal models. This study tells very little about even medium term efficacy of a single dose, unfortunately
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Replying to @AaronRichterman @zeynep
Agree. As
@zeynep said, the 1256 ppl who got one dose of vaccine are interesting, though not randomly selected. With overall event rate of ~168 out of 18,000 in placebo, upper bound of expected cases would be ~12. That's not a lot to work with, but it's not nothing. (1/2)1 reply 0 retweets 3 likes -
There were only ~8 cases in vax arm (out of >18,000), so would expect very few in the 1-dose if they stay protected. I don't think we'll know in time, but a single-round while supplies are limited, and catch-up later, would be a very interesting strategy to evaluate if we did.
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Replying to @roby_bhatt @zeynep
Seems to me the tricky thing will be that the first doses will go to the highest risk groups. Trying to wrap my head around the biases that would come out of single dosing these populations.
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Replying to @AaronRichterman @roby_bhatt
Yes, that's complicated. Elderly are high-risk but healthcare workers aren't that high-risk right now in comparison, to be honest (given PPE usage in hospital). Could imagine subgroup analyses, randomizing single dose among volunteer healthcare workers. I'd sign up in a second.
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(to be clear, if I were HCW... I'd sign up for any version of a single dose study based on the above, given the trade off is doubling the number of vaccinated. We'd know in a few months and can resume as per data).
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Replying to @zeynep @AaronRichterman
I'm an HCW and would also sign up on the spot for this, w/ longitudinal Ab studies (and serial RT-qPCR) etc.
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Replying to @roby_bhatt @zeynep
Yes. Could envision trial of single dose for those prioritized bc high risk for infection by exposure while double dose for those prioritized bc high risk for severe outcome. Agree that hcw lower risk than many assume at this point (discussed that here
)https://jamanetwork.com/journals/jama/fullarticle/2773128 …1 reply 1 retweet 2 likes -
Replying to @AaronRichterman @roby_bhatt
Yeah. Moderna/BnTech went with two dose partly because we weren't expecting this high efficacy and better to clear the hurdle for approval. I get a lot of unknowns but given this data, seems very unlikely one dose would not clear at least the initial 50% bar (probably a lot more)
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Layperson's question: why did the WHO endorse fractional dosing of Yellow Fever vaccine in Africa and Brazil 2016-2019? To this outsider, it seems like a interesting contrast. (But apologies if this is a silly question from a medical/epi standpoint.)
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It was based on two studies; fairly small samples but longer timeframe. But same logic.
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