Thread by @VikiLovesFACS

When is the best time in #pregnancy to get the #CovidVaccine?

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Two studies came out this week that tackle the question. And (bonus!) which vaccine to go for...

🧵...

But first! I should say that all the *safety* data says that it's equally safe to get the vaccine in any trimester.

So the question here is really when it's most *protective* to get the vaccine.

Links to safety data here... 2/

drive.google.com/file/d/1_wHIYX…

The first study, from @EdlowLab, looked at 158 people vaccinated in pregnancy, broken down by vaccine type and trimester of vaccination. 3/

medrxiv.org/content/10.110…

They came back about two months later to see how good of an antibody response the person had made and then again when the baby was born to look at the antibodies in the baby. 4/

People vaccinated with Moderna and Pfizer had more antibodies than those vaccinated with Janssen...

... and so did their babies. 5/

Although the difference was quite subtle, looking at multiple measures of antibody function, people who were vaccinated in the first or third trimester had more functional antibodies than those vaccinated in the second. 6/

Looking now at the babies... those born following vaccination in the first or second trimester had the higher transfer of antibodies... 7/

*But* because antibody levels decline over time, the babies born following vaccination in the first trimester have a somewhat lower *absolute* level of antibody. 8/

The authors conclude...

"These results support vaccination early in pregnancy to maximize maternal protection throughout gestation, without compromising neonatal antibody protection." 9/

A second paper looked at antibody levels in the babies of 171 people vaccinated in the third trimester. Did *when* in the third trimester they were vaccinated make a difference? 10/

ncbi.nlm.nih.gov/pmc/articles/P…

Vaccination earlier in the third trimester resulted in better transfer of antibody across the placenta. 11/

So from all this, when is the best time in pregnancy to get vaccinated against COVID?

If we want to maximise both antibody functionality and post-birth antibody levels in the baby, we would probably say early third trimester...

BUT... 12/

Antibody protection for the baby after birth is really a bonus. The main reason to get vaccinated in pregnancy is to avoid the increased risk of preterm birth and stillbirth that comes with catching COVID in the second half of pregnancy. 13/

Waiting til early third trimester could leave you unprotected for part of this window of vulnerability. So ideally you want to be protected earlier than that.

My view, while case rates are high, is that sooner is better. 14/

Bonus! My colleague @jackie_parchem is surveying her O&G friends to see what they think about timing of boosters in pregnancy. Let's see if they think they same...

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https://twitter.com/jackie_parchem/status/1461350795769573382?s=20