A question I get asked *a lot* is…

“What are the long-term effects on babies born after #COVID19 #vaccination in #pregnancy?”

So let’s talk about what we know… 🧵
Let’s start by looking at the effects at birth. We now have eight large datasets from four countries looking at almost 79,000 people vaccinated in pregnancy. The outcomes for the babies are all normal. 2/
(The CDC has recently put out data from 2 more US studies, bringing the total to 10. But there is some overlap between the participants in these studies and the ones quoted above, so I didn't add those in as unique participants.)

From V-safe... 3/

And from the Vaccine Safety Datalink... 4/

If you would like to read more about this, there's a summary here. And if you want to read more, you can click the links to get to the primary papers... 5/

So all these babies look normal at birth. But is there a possibility that something will emerge in these healthy babies, months or years down the line? 6/
Obviously we don’t yet have data on what these babies will be like at, say, two years old, but we can use what we know about vaccination in pregnancy to make some predictions, with high confidence. 7/
Like the other vaccines routinely given in pregnancy, mRNA COVID19 vaccines do not cross the placenta. So they don’t actually get into the baby. This reduces the risk of an unexpected effect a lot. 8/

And from this, we might say that we expect the long term effects of these vaccines on babies to be similar to other vaccines we give in pregnancy… and we’ve never detected any bad ones.

More on this here... 9/

But finally, one thing I think is worth remembering if you’re pregnant right now is that there’s something going round at the moment which *can* have a long-term impact on the health of your baby.

COVID. 10/
We know that catching COVID in late pregnancy makes it more likely that you and your baby will suffer from a number of poor outcomes.

One of these is preterm birth. Babies who are born preterm are more likely to grow up with various disabilities. 11/

So just thinking about long-term outcomes for babies, we have every reason to expect the healthy babies born after vaccination in pregnancy will remain healthy.

On the other hand, COVID does pose long-term risks to babies and vaccination can prevent them. 12/12

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More from @VikiLovesFACS

8 Sep
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


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/

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/
Read 6 tweets
17 Aug
On holiday without much in the way of internet, but wow! My notifications blew up when I hit some WiFi this afternoon. A few points on this… 1/
First, I’m surprised neither of them checked our national guidance, which is set out in detail for medical professionals here… 2/

Or the guidance from @RCObsGyn and @MidwivesRCM, which makes a clear recommendation that #pregnant people get the #COVID19 #vaccine. You can find it here… 3/

Read 7 tweets
13 Aug
New data from the V-safe pregnancy registry on the safety of #COVID19 #vaccines in #pregnancy!

👉🏻 2456 people vaccinated before 20 weeks of pregnancy

👉🏻 Followed up to 20 weeks

👉🏻 No increased risk of miscarriage following vaccination.


This is a follow-up to this older study in the same cohort. The older version of the study showed no increased risk of miscarriage following vaccination, but the follow-up time was shorter (10-12 weeks). 2/

Although the data from this study was reassuring, the limited follow-up time made it difficult to exactly calculate the miscarriage rate following vaccination, so an estimate was used.

I’ve discussed that here… 3/
Read 11 tweets
10 Aug
Who's been waiting for UK data on the safety of #COVID19 #vaccines in #pregnancy? 💉🤰🏽🇬🇧🤔


Well now we have some!

(TLDR: No concerns arising from this study)... 🧵

This study looked at people coming to give birth at St George's hospital in London between March 1st and July 4th 2021.

141 had had at least one dose of a COVID vaccine

1187 were unvaccinated. 2/
(And for those always on the hunt for data about the AstraZeneca vaccine in pregnancy... 13 of the vaccinated people had had AZ.) 3/
Read 7 tweets
19 Jul
After I wrote this thread about the potential effects of COVID vaccination in pregnancy and the lack of such effects in other vaccines, perinatal epidemilogist @deshaynef got in touch to tell me about some work she has done in this area... 🧵
Her group has published two papers doing 3-5 year follow-up on the babies of people vaccinated against flu in pregnancy.

👉 Flu vaccination in pregnancy was not associated with adverse outcomes in children later on. 2/
Read 5 tweets
19 Jul
"I'm #pregnant and I want to get the #COVID19 #vaccine to protect myself and my baby. But should I wait until after 12 weeks?"

Two studies have looked at pregnancy-specific adverse events following COVID-19 vaccination in the first trimester of pregnancy.

Both found no increased risk of miscarriage.... 2/


The other thing that is a theoretical worry in the first trimester is a high fever (more than 39C for more than 24h) affecting the baby's development.

Although mild fevers are a common side-effect of vaccination, a fever as severe as this is really uncommon... 3/
Read 11 tweets

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