Thread by @chrischirp

Quick thread on the Astra Zeneca (AZ) covid vaccine since it's been in the news today.

TLDR there isn't a new "smoking gun", the AZ vax was one of first and cheapest, it saved millions of lives globally, there are better vax out there now, adapted to new variants 1/9

the AZ vaccine was one of the first approved at the end of 2020, cheaper than Pfizer, and - importantly - easier to administer in lower resource settings as it didn't require super low temperatures for storage 2/9

In most countries it was first rolled out in older adults. As it was rolled out in younger adults, a *very rare*, serious, side effect was noticed - it could cause deadly blood clots

This was spotted quickly and studied. Vax monitoring did its job. 3/9

Many countries then (this is mid 2021) restricted the AZ vaccine to older populations *as long as they had access to other vaccines (e.g. Pfizer)*,

the AZ vaccine remained *far* safer than catching covid (even if just considering likelihood of getting blood clots). 4/9

Because AZ was affordable and (relatively) easy to roll out at scale, (particularly relevant in low and middle income countries), it was widely used in that first crucial vaccine year of 2021.

Its efficacy has been *widely* studied and it reduced severe infections by 90%. 5/9

Imperial College estimated that together, Covid vaccines saved about 20 million lives by the end of 2021.

A further study by vaccine type, estimated that the AZ vaccine saved over 6 million lived by the end of 2021. 6/9

For updating the vaccine for new variants, the way the AZ vaccine is made means that it takes longer & is harder to do than mRNA vaccines (like Pfizer and Moderna).

3 years on, there are better vaccines out there, that are cheaper, (even) safer & quicker to update. 7/9

The AZ vaccine is no longer needed and has been discontinued.

This is NOT nefarious and it does NOT negate its vital role in 2021 in saving millions of lives. 8/9

For a more detailed (and expert!) explanation, please watch out for a new blog by @sheencr which will come when she has time to write it!
In the meantime, please don't let the anti-vaxxers get to you. 9/9

PS referenced articles here:








journals.plos.org/plosmedicine/a…
bmj.com/content/374/bm…
frontiersin.org/journals/publi…
airfinity.com/articles/astra…
thelancet.com/journals/lanin…

PPS thanks as ever to my brilliant @IndependentSage colleagues for their knowledge and insights.