Thread by @VikiLovesFACS

A bunch of people have been in touch about this paper. Has a review of the evidence really raised questions about the safety of the Pfizer #COVID19 #vaccine in #pregnancy?

TLDR: No… 🧵

https://twitter.com/simonthornley30/status/1454946429495963659

The paper purports to present a reanalysis of the V-safe pregnancy registry data to the end of February. You can find the original report (which concluded no increased risk of pregnancy complications following vaccination) here… 2/

nejm.org/doi/full/10.10…

But before we get into the details of what’s been done here…

There is no need to scry the six-month-old data from Shimabukuro! It was difficult to interpret because of the limited follow-up time, but *luckily* we now have longer follow-up data… 3/

nejm.org/doi/full/10.10…

The longer follow-up (which also has more participants) allows us to accurately calculate the week-by-week miscarriage rate following vaccination.

It’s the same as normal. 4/

https://twitter.com/vikilovesfacs/status/1426068225046024192

So what’s going on with this reanalysis you’ve been asking about? It’s a decent length paper in a peer reviewed journal, so I was expecting something reasonably sophisticated… 5/

But actually, it boils down to the argument we saw circulating on social media back in June.

In short, if you ignore almost all the people who are still pregnant, the miscarriage rate looks artificially high. 6/

Here’s some more detail on why we can’t ignore people who are still pregnant when calculating miscarriage rates, and some recalculations showing what happens if you add them back in (the miscarriage rate looks normal again)… 7/

https://twitter.com/vikilovesfacs/status/1410508758099369984

It’s surprising that such a basic error should have made it past peer review (though I don’t actually know this journal: scientist friends, is it even legit?)… 8/

But the consensus, based on the V-safe data we’ve discussed here, plus a further nine studies, is that #COVID19 #vacination in #pregnancy is not associated with increased risk of miscarriage or any other pregnancy complication. 9/

If you would like to read the studies yourself, you can find them (and more!) here… 10/10

drive.google.com/file/d/1_wHIYX…