Thread by @VikiLovesFACS

This study looked at the effectiveness of the Pfizer #COVID19 #vaccine in #pregnancy.

👉🏻 96% effective vs. any infection

👉🏻 97% effective vs. symptomatic infection

👉🏻 89% effective vs. hospitalisation

1/

nature.com/articles/s4159…

A few additional points…

Why is effectiveness vs hospitalisation lower than against all infection? This is the opposite of what we see in larger studies of the whole population, eg. this PHE data… 2/

media.tghn.org/articles/Effec…

Very few people were hospitalised (5/10,861 in the unvaccinated group compared to 0/10,861 in the vaccinated group).

This means the confidence interval for effectiveness vs hospitalisation was wide (43 - 100%) which is likely to have lowered the central estimate. 3/

It’s also important to note that the main variant circulating in Israel when this study was done was the alpha variant, so this tells us about vaccine effectiveness against that.

But… 4/

… the finding that vaccine effectiveness in pregnant ppl is similar to those who are not pregnant means that we can probably assume that vaccine effectiveness against delta in pregnant ppl (which we don’t know yet) is similar to that in the general population (which we do.) 5/5

Correction! Sorry I was reading from the wrong table when I gave the absolute numbers of hospitalisations. It was actually 25/10,861 in the unvaccinated group compared to 11/10,861 in the vaccinated group. The effectiveness is given correctly, though, as 89%.