You know what else does not take into account the habits of each individual post vaccination, ... or such things like how the individual isolated? Stage III trials.
And do you know where the WHO got the 'efficacy of 63.09% against symptomatic SARS-CoV-2 infection' data from? From AstraZeneca's Stage III trials.
Stage three trials did however take a cross section of the community to a point. Not just focus on over 70s, so the numbers presented in that study only relate to that age group. That being said it is teh most vulnerable group so it's obvious why the focus.
Our results and those seen in the phase III clinical trials show similarities.
So overall the phase 3 trials were the same result.
Also this study was done on subjects self assessing, phase 3 was subjects were clinically assessed.
Misclassification is also likely to be a factor in this study. Symptoms are self-reported and may not be specific to covid-19 without clinician diagnosis. Furthermore, individuals may falsely report symptoms to have a test, which will include asymptomatic individuals in the symptomatic analysis and means that symptom onset dates are incorrect.
and this;
Failure to exclude those with past infection because of low testing rates in wave 1 is another possibility.
I mean it is comparing Apples and Oranges anyway as the Phase 3 trials are overall from 18-90 year olds and this study is only 70+. Also phase 3 studied Asymptomatic as well as Symptomatic, where this study focused only on Symptomatic.
The vaccine still does most of what it should, is safe and anyone over 65 should take it ASAP given no other options.
From memory the US Stage III trial data was better again, likely as much due to the different prevailing conditions.
That's where I got the peak of 79%. But yes the WHO data is based on the UK/Brazil trials.
PS I remember from the trials that there was some controversy over AZ not being trialed on many over 65, probably why this further study was taken.