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Oxford vaccine shows sustained protection of 76% in 3-month gap til second dose

ox.ac.uk

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Re: Oxford vaccine shows sustained protection of 76% in 3-month gap til second dose

#51

Post by StavrosK »

Eric_WVGG wrote: post #23
reportingsjr wrote: post #18

Earlier quoted context omitted.

That is not what any of the vaccine studies have said so far. I haven't read this one, but I bet it also doesn't say this. The stated efficacy/protection percentages that have been presented so far have been for the reduction of _symptoms_. There haven't been any studies on vaccines preventing infections, probably due to lack of resources for testing everyone in a trial multiple times.

IANAD but I'm nearly positive you're incorrect. I spent last night puzzling over what "efficacy" means vis a vis this video: https://www.technologynetworks.com/immunology/videos/covid-1... The author explains that the efficacy number is derived from the the number of the number of people in the control/placebo group infected divided by the total number of infections in the study. 76% efficacy means that, for a given…

> The author explains that the efficacy number is derived from the the number of the number of people in the control/placebo group infected divided by the total number of infections in the study.

Wouldn't that make a vaccine that does nothing 50% effective, instead of 0% effective (which is what one would expect)?

Re: Oxford vaccine shows sustained protection of 76% in 3-month gap til second dose

#52

Post by akiselev »

hutzlibu wrote: post #38
Eric_WVGG wrote: post #23

Earlier quoted context omitted.

IANAD but I'm nearly positive you're incorrect. I spent last night puzzling over what "efficacy" means vis a vis this video: https://www.technologynetworks.com/immunology/videos/covid-1... The author explains that the efficacy number is derived from the the number of the number of people in the control/placebo group infected divided by the total number of infections in the study. 76% efficacy means that, for a given…

It is so frustrating, trying to figure out at least a bit of whats going on and understanding some numbers, but apparently I cannot do this, without having to dive into papers, too? There is so much confusion and missinformation flying around, when even here on HN there is discussion about the meaning of basic numbers. (but please carry on discussing it)

To be clear, this isn't some settled math like basic algebra or science like Newtonian physics - this is cutting edge stuff at the intersection of medicine, public health, and biotechnology. Experts disagree about the nuances of measuring the efficacy of drugs, vaccines, and therapeutics so throw in the glaring ethical concerns into the mix and you have a recipe for a complex field. It's rare (unheard of?) to find a clinical trial where the company (or their CRO) scientists didn't sit down with FDA regulators and negotiate over key features & risk indicators, benchmarking, patient selection, and so on because they bring expertise the FDA is unlikely to have.

It's very difficult to get even a basic grasp of the details because you need to grok some complex statistics, biology, and public health to really dig in. Journalists sure aren't going to get the nuances so of course you have to read the academic literature.

Re: Oxford vaccine shows sustained protection of 76% in 3-month gap til second dose

#53

Post by Eric_WVGG »

StavrosK wrote: post #51
Eric_WVGG wrote: post #23

Earlier quoted context omitted.

IANAD but I'm nearly positive you're incorrect. I spent last night puzzling over what "efficacy" means vis a vis this video: https://www.technologynetworks.com/immunology/videos/covid-1... The author explains that the efficacy number is derived from the the number of the number of people in the control/placebo group infected divided by the total number of infections in the study. 76% efficacy means that, for a given…

> The author explains that the efficacy number is derived from the the number of the number of people in the control/placebo group infected divided by the total number of infections in the study. Wouldn't that make a vaccine that does nothing 50% effective, instead of 0% effective (which is what one would expect)?

Well, let's see… say you had 2000 participants in the trial, 1000 with a junk vaccine, and 1000 with placebos.

Furthermore, let's say you had 200 infections, split equally between the junk and the placebo.

So yeah, 100 / 200 = 50% effective. A coin toss, which is to say, no better or worse than not getting the vaccine.

Again, this isn't measuring "what one would expect" (how many vaccinated people, exposed to the virus, get the disease), it's "what proportion of vaccinated people get sick relative to unvaccinated people." (again IANAD)

Re: Oxford vaccine shows sustained protection of 76% in 3-month gap til second dose

#54

Post by carschno »

jMyles wrote: post #35
renewiltord wrote: post #28

Earlier quoted context omitted.

> We can't measure that directly because we can't just expose a bunch of folks to Covid and hope for the best. We can, but medical ethics hasn't caught up yet. I would participate in a challenge trial, for instance.

> I would participate in a challenge trial, for instance. Me too. And nearly everyone I know in my risk tier. We had an entire globe of low-risk people willing to be part of the most acute spread, whether for research, for personal immunity, or to be able to isolate for a defined time to protect loved ones, and we squandered it in favor of pseudoscientific horizontal interdictions like lockdowns. It's really an incre…

If the sample consists of volunteers, it's hardly random. In particular, given that these volunteers are "low-risk people", it means that the results of this experiment will yield virtually no useful conclusions for the higher-risk groups

Re: Oxford vaccine shows sustained protection of 76% in 3-month gap til second dose

#55

Post by alkonaut »

robotmay wrote: post #43
the_mitsuhiko wrote: post #26

It’s interesting how the Astra Zeneca vaccine is such an emotional topic. In the UK it’s seen as the greatest weapon against the pandemic, in the US it is not playing much of a role and in the EU public perception is super negative.

The EU seems to keep bringing focus back onto the over-65 efficacy. The German government has said it shouldn’t be used on over-65s, Poland has now followed, and Macron has been out in the press regurgitating incorrect statistics he misread somewhere (saying it’s only 10% effective, rather than the correct stat being that the age group made up around 10% of test subjects). Personally I think the UK approach is the wa…

Countries that have a supply of Pfizer/Moderna as well as AZ can understandably be more cautious with AZ to over-65 at least early on. It’s just a matter of assigning the right vaccine to the respective groups, e.g Pfizer to the elderly and AZ to healthcare workers.

In a month or two there will be more data, but in Q2 there will also be more supply of Pfizer and Moderna in the EU.

The EU can be cautious with AZ to elderly now because it can afford to due to large quantities of rna vaccine.

A few thousand elderly will die waiting for the slow buildup of rna delivieries while AZ could be made available. That’s the obvious drawback of this caution.

Re: Oxford vaccine shows sustained protection of 76% in 3-month gap til second dose

#56

Post by StavrosK »

Eric_WVGG wrote: post #53
StavrosK wrote: post #51

Earlier quoted context omitted.

> The author explains that the efficacy number is derived from the the number of the number of people in the control/placebo group infected divided by the total number of infections in the study. Wouldn't that make a vaccine that does nothing 50% effective, instead of 0% effective (which is what one would expect)?

Well, let's see… say you had 2000 participants in the trial, 1000 with a junk vaccine, and 1000 with placebos. Furthermore, let's say you had 200 infections, split equally between the junk and the placebo. So yeah, 100 / 200 = 50% effective. A coin toss, which is to say, no better or worse than not getting the vaccine. Again, this isn't measuring "what one would expect" (how many vaccinated people, exposed to the vir…

Kind of seems odd, given that you can never have 0% efficacy (unless your vaccine somehow caused every vaccinated person to get the disease instead of a non-vaccinated person). It seems like you're wasting half your "spread", basically.

If you measured efficacy as "1 - (vaccinated infections / unvaccinated infections)", it would be much more intuitive, and you could even get a bit of negative efficacy in the case where your vaccine did nothing.

Re: Oxford vaccine shows sustained protection of 76% in 3-month gap til second dose

#59

Post by krzyk »

alkonaut wrote: post #55
robotmay wrote: post #43

Earlier quoted context omitted.

The EU seems to keep bringing focus back onto the over-65 efficacy. The German government has said it shouldn’t be used on over-65s, Poland has now followed, and Macron has been out in the press regurgitating incorrect statistics he misread somewhere (saying it’s only 10% effective, rather than the correct stat being that the age group made up around 10% of test subjects). Personally I think the UK approach is the wa…

Countries that have a supply of Pfizer/Moderna as well as AZ can understandably be more cautious with AZ to over-65 at least early on. It’s just a matter of assigning the right vaccine to the respective groups, e.g Pfizer to the elderly and AZ to healthcare workers. In a month or two there will be more data, but in Q2 there will also be more supply of Pfizer and Moderna in the EU. The EU can be cautious with AZ to el…

> Pfizer to the elderly and AZ to healthcare workers.

With Pfizers (and Moderna) ~95% efficacy and AZ at 60% I would give AZ to only those that want to jump the line or as the last resort.

You don't want doctors to spread COVID (40% vs 5% that can spread is huge).

Poland wants to give AZ to teachers, a group that has contact with many children (which have contact with their families) - this is poor thinking. AZ should go to people that don't have much contact with others, e.g. unemployed or volunteers.

Re: Oxford vaccine shows sustained protection of 76% in 3-month gap til second dose

#60

Post by renewiltord »

throwaway2245 wrote: post #47
renewiltord wrote: post #28

Earlier quoted context omitted.

> We can't measure that directly because we can't just expose a bunch of folks to Covid and hope for the best. We can, but medical ethics hasn't caught up yet. I would participate in a challenge trial, for instance.

A randomly controlled challenge trial would involve deliberately infecting scores of unvaccinated people, putting them at risk, along with anyone involved in the procedure and anyone they come into contact. It would mean handling live virus, which requires a Biosafety Level 3 facilities. And, it's not going to get your vaccine approved any quicker.

See, this is a classic example. You need BSL3 facilities if you want to have a hundred people have it. But the alternative is 27 million people getting it in planes, boats, and buses - none of which are BSL3. That part is okay.

Quite the example of the asymmetry. If you engage with the problem you have to operate absolutely perfectly. Way better not to engage with it and kill a few hundred thousand people. After all, no one can blame you for that part.

And of course it's not going to get the vaccine 'approved' quicker because yeah, 'approval' is also subject to the same people. But it will let us know if it works and whether it hurts.

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