The Astra Zeneca Covid vaccine saved millions of lives globally

Better vaccines have now emerged - but the Astra Zeneca vaccine played a crucial role in that first vaccine year of 2021

*** very quick post adapted from my Twitter thread ***

The Astra Zeneca (AZ) Covid vaccine has been in the news today with scary headlines. But they are needlessly scary headlines. Fundamentally the situation is this: there isn't a new "smoking gun"; the AZ vaccine was one of first and cheapest vaccines; it saved millions of lives globally; there are better vaccines out there now, adapted to new variants.

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.

In most countries it was first rolled out in older adults (as they were the most at risk population). As it was rolled out in younger adults, a *very rare*, serious, side effect was noticed - it could cause deadly blood clots in the first few weeks after the first dose. This was spotted quickly and studied. Vax monitoring did its job.

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).

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%.

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.

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). Three years on, there are better vaccines out there, that are cheaper, (even) safer & quicker to update.

The AZ vaccine is simply 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.

My Indie SAGE colleague, Prof Sheena Cruickshank, (an expert immunologist) will add her expertise to this short post with one of her own once she has time - so please do watch out for that! Also I want to say thanks to my other brilliant Indie SAGE colleagues for helping me get my thoughts in order too!