Thread by @chrischirp

THREAD on vaccine effectiveness:

Public Health England released its updated report on real world effectiveness of Pfizer & AZ in England this week.
assets.publishing.service.gov.uk/government/upl…

I thought would be helpful to explain what they found...

TLDR: pretty good! 1/9

Firstly, both vaccines work almost equally well, so going to treat them as one in below.

Secondly, will focus on effect of ONE dose in OVER 80 year olds (most data!).

Effectiveness is higher in younger people and after second dose. 2/9

Right, so let's consider two lots of over 80s - 100,000 people in each group.

One group is unvaccinated and the other is more than two weeks out from their first dose.

(There seems very little real world protection for first two weeks after vaccination!!) 3/9

In the unvaccinated group, about 300 people might get symptomatic Covid. Exactly how many depends on how much Covid there is around, but let's go with 300 for now (0.3%).

Of those 300, 45 might need to go to hospital with Covid and 40 might die from Covid. 4/9

So what about the over 80s who've had one dose of vaccine?

Well, it offers about 60% protection from getting symptomatic Covid (ie feeling sick from Covid).

So, instead of 300, only about 120 out of the 100K might get sick with Covid. 5/9

For those 120 vaccinated people with Covid, they get *further* protection from needing hospital (35%-45%) or dying (55%).

So, only 10 out of the 120 might need hospital, and only 7 out of the 120 might die. 6/9

So *overall*, after one dose, an 80+ yr old person is 75%-80% less likely to need hospital from Covid and 80%-85% less likely to die from Covid compared to someone who has not been vaccinated.

This is GOOD! 7/9

As a comparison, seat belts + air bags are ~70% effective at preventing death from car accidents.

pubmed.ncbi.nlm.nih.gov/21720604/

You definitely want to wear a seat belt & have an air bag, but you still want to drive safely!

After 1 dose of vaccine you still want to be sensible. 8/9

Plus, just as you drive safely to protect others on the road as well as yourself, being sensible with Covid precautions protects those who haven't been vaxxed or for whom it doesn't work well (e.g. some cancer patients), because the vaccines do reduce transmission too. 9/9

PS H/T to @adsquires for the seat belt analogy :-)