Oxford/AZ Vaccine - Explainer

[PurplePansy05]

Please could someone who understands more about this vaccine explain the below?

I'm reading on Sky News:

"A statement from the Department of Health said: "The JCVI has advised the priority should be to give as many people in at-risk groups their first dose, rather than providing the required two doses in as short a time as possible.

"Everyone will still receive their second dose and this will be within 12 weeks of their first. The second dose completes the course and is important for longer term protection."

Source:
news.sky.com/story/covid-19-oxford-astrazeneca-vaccine-approved-for-use-in-uk-12155958

So this vaccine is said to have a 62% efficacy with two full doses and up to 90% with half a dose followed by a full dose which was a random discovery. Is the latter how it was approved for use by the MHRA?

If so:

1. Why is it recommended to have one full dose asap (presumably it is one full dose?)

1. Why is getting the one full dose to as many people as possible the main focus? Surely if both doses are required for it to work then both are important? It doesn't work on one dose, does it?

1. Final question, if the efficacy is 62%, what does this mean in practice? That it prevents 62% of vaccinated people from getting ill with COVID-19?

TIA.

1. Why is it recommended to have one full dose asap (presumably it is one full dose?)

We want as many (vulnerable especially) people vaccinated as quickly as possible when our covid levels on circulation are so high. There wasn’t enough data to approve the half dose-full dose regime so it’s a full dose.

2. Why is getting the one full dose to as many people as possible the main focus? Surely if both doses are required for it to work then both are important? It doesn't work on one dose, does it?

One dose gives some protection, the second dose gives more. I read this morning that delaying the second dose for three months rather than three weeks will give better protection although that data is not published yet.

3. Final question, if the efficacy is 62%, what does this mean in practice? That it prevents 62% of vaccinated people from getting ill with COVID-19?

Yes, that’s right.

Third question

I thought it was prevented 62% catching it, but prevented serious illness in the others

No hospitisation in any of the vaccinated groups who did catch the virus

1. To get as many people partially vaccinated in as short a time frame as possible. They will have calculated that this is a quicker way of reducing hospitalisations/deaths, rather than give people two doses in a shorter timeframe.

1. It's not black or white. Rather that one dose gives you quite a lot of protection, and two doses gives you a bit more.

1. When tested, they have two groups. One is injected with the AZ vaccine (goroup A), the other (group B) a non-Covid vaccine as a control. They then compare the two groups to see whether group A gets fewer incidences of Covid than group B. If group A gets statistically significantly fewer cases over a few months than group B, it is considered effective.

If you have 10,000 in each group, and 10 people in group A get infected, whereas 20 people in group B get infected, it is said to be 50% effective.

Using statistics you can work out how likely the result is due to chance alone. I won't go into how it's done, but safe to say that with 10,000 in each group the chances of the result being down to luck are tiny.

They can also not only look at cases in each group, but deaths/hospitalisations and I believe the AZ vaccine is very effective at preventing severe illness.

The vaccine prevented 62% of people who received it in the trials from getting infected with COVID.

BUT it also protected everyone who received it from becoming ill enough to require hospital treatment, and nobody who received it died of COVID.

Clever scientists! 😀

So in other words, full evidence hasn't been published yet, but the reasons why they're rolling it out the way they are are:

• because this vaccine even after one full dose provides immunity to some people; and
• the rest is likely to get a lighter (cold-like?) illness after one dose?

Meaning neither of the above will need to be hospitalised and so the more people vaccinated with one dose, the sooner we'll be able to move on with our lives?

That's it.

Ignore my previous number 3 answer, I’ve totally misread what was written. Trying to listen to the radio at the same time.

That 62% efficacy means a 62% percentage reduction in disease in people who have been vaccinated compared to those who haven’t.

Thank you all. I'd like to think I'm fairly with it and I've been following all the developments, however I didn't feel like these issues have been explained clearly by the Govt/media/Oxford-AZ, anyone really. I have now read some more comments from prof. Gilbert which are very helpful.

Your comments have really helped, thanks again. I suspect there is quite a number of people out there who might be confused about thus vaccine.