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Comment by theflowerpot | Hacker News Reader

Recent reports mention 95% effectiveness for the Oxford-AstraZeneca vaccine if the doses are taken 3 months apart, which would be great if confirmed.

https://www.businesstoday.in/current/economy-politics/oxford...

https://www.thetimes.co.uk/article/covid-vaccine-boost-for-m...

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they always seem to find additional data supporting this or that. Idk, to me it seems like their reporting is literally all over the place, how did they confirm 95% effectiveness? what's the trial-size, is it also 30k participants like the others? What's the age-distribution of those that took part in this 3-months trial, there are a ton of unknowns with that vaccine, and neither Oxford nor AZ are particularly helpful with clearing those doubts atm.

They gave more data to MHRA. Let's not forget that the data used for the Lancet publication was from November 4th.

And the Jenner Institute in Oxford doesn't do preprints or press releases for data, they go for publications (so that takes more time).

That said, I expect the missing information to appear in MHRA's guidance notes.

They have in many ways been more rigorous and transparent than other vaccine trials (weekly swab testing of all subjects, publishing the paper first rather than in the media first, being honest about mistakes made). They don’t control the media reporting.

That said it seems the group who received smaller doses by mistake was only 1300, not sure where they got the data on 12 weeks but presumably it’s also a small number or they’d be going with that for everyone.

Things should become clearer over time and I hope they can shift to the smaller doses first as it’d give us double the number of initial vaccinations when supplies are limited.

the just tried to fit in numerous trials into a single trial, whereas Biontech/Pfizer and Moderna were super clear about their trial-architecture and data (same 2-dose regime, given 3 weeks apart), we seem to have a ton of small trials with different data for that Oxford/AZ vaccine. Those 1300 participants who got the half dose full dose vaccine also turned out to be significantly younger than the other group who got the two full-dose regime, making those two groups really difficult to compare (apart from the fact that they were also differing in size)

Now we have a new number out there, 90% if the two doses are given 3 months apart, does anyone here now what the trial-size was? the age distribution? The statistical significance for that finding?

Don't forget that the BioNTech/moderna trials weren't really comparable - they relied on self-reported symptoms to trigger checks for infection. That is likely to lead to a higher apparent efficacy at the same underlyng efficacy.

By now it's clear that for all three vaccines regardless of the exact efficacy of the vaccine, the chances of getting a severe case is greatly diminished. It's at least plausible that getting a vaccine reducings the severity of an infection in general; specifically that it might push what would otherwise have been a mild case into the asymptomatic (but infected) category. I don't know how large that group is, but given how many mild cases there are, it could be quite sizable. And those cases would not have been included in moderna and biontech/pfizer's efficacy numbers, but would have been included in the oxford/AZ trial's numbers.

So while I'm no expert in any of this, I think it's at least fair to say that it's not trivial to compare the efficacies reported from the two mRNA vaccines to that of the oxford/AZ vaccine, because of this difference in methodology. Including vs. mostly excluding asymptomatic cases will affect the numbers.

The point being? All of these trials have their limitations; the oxford/AZ trials may have had bumps (but nothing all that serious sounding), but they also have extra data in the form of asymptomatic cases. The comparison isn't straightforward.

that 62% number is for symptomatic cases, I think it was around 50% for asymptomatic cases - the different efficacy-rates are fairly comparable

That is a good point, I'd forgotten that bit ;-).

(ref: https://www.thelancet.com/journals/lancet/article/PIIS0140-6... vs. e.g. https://www.nejm.org/doi/full/10.1056/NEJMoa2034577 )

From the news report it's 95%, not 90%. Presumably the data about sample size etc. will be available when they publish. You can't reasonably expect that level of detail from a news article reporting prior to publication.

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