Vaccination roll out schedule.

[Bruce Stephens]

on the basis that most of the protection comes from the first dose.

Only we don't know that with much confidence (since it's not been tested). I like the idea in principle (and especially if we knew that it didn't matter much when the second dose came) but it feels a bit risky in real life. (Let's hope the Oxford/AstraZenica vaccine is approved since I think there's a lot more doses of that in the short term.)

 

[trophywench]

It is true that we apparently get 51% immunity from the first dose of the Pfizer which increases to 90% after the second one and then that ramps up to 95% - so 51% is certainly more than 50% of 95, which would be 47.5%. But 'MOST' ??? I don't think so, ducky.

 

[Robin]

It is true that we apparently get 51% immunity from the first dose of the Pfizer which increases to 90% after the second one and then that ramps up to 95% - so 51% is certainly more than 50% of 95, which would be 47.5%. But 'MOST' ??? I don't think so, ducky.

The article I read said that the 51% was an average, with hardly any protection during the first week, then rising steadily. The theory is, that the measurement of over 90% after the second dose, is taken before the extra protection given by second dose has had time to develop, therefore it must all be down to the first dose.

 

[Docb]

Anybody know what these percentages mean? Do 100% of the people get 90% protection or do 90% of the people get 100% protection?

 

[Bruce Stephens]

Anybody know what these percentages mean? Do 100% of the people get 90% protection or do 90% of the people get 100% protection?

I think it's more likely the first, but I don't think the actual data tells you.

For the vaccine efficacy it's very simple (for most of the trials, and if I'm understanding it correctly): half of the people got the vaccine and half got a placebo of some kind. Then you count the people who end up getting symptomatic infection (or whatever the goal is), and if 90% of those were in the placebo arm then your vaccine has 90% efficacy.

(The Oxford/AstraZenica trials are more complex as I understand it. I think they gave the vaccine to more than half, and I think there are multiple (differently organised) trials which they combined.)

I don't remember how the 51% after a single dose was calculated. Maybe measuring antibodies or something? (Seems unlikely you'd have enough people getting infected between the two doses to make it possible to give a good estimate that way.)