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Immunologist working on pregnancy at @ImperialCollege | equality and diversity in STEM | she/her | Because VikiLovesNKCells was too long for Twitter
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May 5 10 tweets 7 min read
@BerryTartlet @DrLoupis Yes, this is quite an old document. A timeline of UK policy on this might help you.

8 - 31 Dec 2020. Vaccines approved, but using the same exclusions as the trials - no-one who is or could be pregnant. That’s the document you’re looking at there. 1/ @BerryTartlet @DrLoupis Also worth noting that even at that point, there’s nothing saying it’s not safe, only pointing out that we don’t have any evidence yet. 2/
Jan 29 11 tweets 7 min read
@jtmayes3 @kevinault Let’s begin by taking the 172,000 number at face value. About 190,000 ppl have been vaccinated during pregnancy in the US. So if that were true it’s a miscarriage rate of 90%…

1/… @jtmayes3 @kevinault Quite apart from being not plausible, it’s straight up impossible. Miscarriages by definition happen before 20 weeks and about half of those vaccinated were vaccinated after 20 weeks. It was too late for them to have a miscarriage. 2/
Jan 20 6 tweets 4 min read
2,126 couples #TryingToConceive between Dec 2020 and Sep 2021…

👩‍❤️‍👨💉 #CovidVaccination made no difference to per cycle chance of #pregnancy

👩🏻🦠 Infection of female partners made no difference…

👦🏽🦠… but in males ⬇️ chance of pregnancy for ~60d.… The finding that #CovidVaccination does not affect #fertility mirrors what we have already seen in IVF settings, but it is good (if unsurprising!) to see it confirmed among those #TryingToConceive the old fashioned way! 2/…
Jan 13 8 tweets 4 min read
*New data* from 79,148 ppl giving birth in Scotland Mar 20 - Oct 21.

🦠 #COVID ⬆️ risk of stillbirth or neonatal death by ~4x, and preterm birth by ~2x

💉 #CovidVaccination protects against COVID and is not associated with poor #pregnancy outcomes. 1/… This gives us some homegrown data on vaccine effectiveness in pregnancy, including in the delta wave. Roughly speaking, vaccination reduces the risk of...

Any infection by 30%

Hospitalisation by 72%

ICU by 94%

Jan 7 18 tweets 5 min read
Does #CovidVaccination cause changes to #periods?

I know ppl have been wondering about this! But up to now the data we had was pretty preliminary. However, with a large, prospectively collected dataset out yesterday, I think it’s time to start putting it all together.... 🧵 Here’s some more on that new study. In short, people who received both doses of the vaccine in a single menstrual cycle found their period came a couple of days late. But it was back to normal a couple of cycles later, so the change was temporary. 2/

Jan 6 13 tweets 3 min read
Does #CovidVaccination cause changes to #periods? Biggest and best study so far...

In summary: on average, periods are delayed by ~half day by dose 2 of the vaccine, and delayed by ~2 days if you get both doses in the same cycle. But it's temporary! 🧵… 3959 spontaneously cycling ppl logged at least 6 consecutive cycles with tracking app @NaturalCycles.

2403 were vaccinated. Taking them all together, the average period came 0.64d late after dose 1 and 0.79d late after dose 2. No difference in length of period. 2/
Dec 16, 2021 5 tweets 3 min read
If you get the #CovidVaccine while you are #pregnant, what cross the placenta? 🤔

This new preprint looked at 19 people vaccinated in pregnancy, and their babies, to find out... 🧵… 👉🏻 Vaccine mRNA and Spike protein were not detectable in placenta or cord blood.

👉🏻 Anti-spike IgM was not present in cord blood (which it would be if the babies had made their own response to the vaccine).

Two previous studies also found this... 2/

Nov 25, 2021 6 tweets 3 min read
📢 The first large scale UK data on the safety of #CovidVaccine in #pregnancy is out today from @UKHSA !

In people giving birth between January and August, 24,759 of whom were vaccinated...

🗝️ No difference in stillbirth rate between vaccinated and unvaccinated... 1/ 🗝️ No difference in babies with low birthweight between vaccinated and unvaccinated... 2/
Nov 19, 2021 15 tweets 5 min read
When is the best time in #pregnancy to get the #CovidVaccine?


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/…
Nov 17, 2021 13 tweets 3 min read
How can we know that #COVID19 #vaccines will not harm #fertility? Could an effect unexpectedly appear years into the future?


🧵... Let’s start with the data we have on fertility right now.

👉🏻 No reduction in pregnancy rates in vaccinated (vs unvaccinated) ppl in clinical trials.

👉🏻 Egg quality, fertilisation rates and pregnancy rates are the same in vaccinated and unvaccinated IVF patients. 2/
Nov 17, 2021 7 tweets 4 min read
"I'm #pregnant, and I've been offered a #CovidVaccine #booster. Should I accept?"

@RCObsGyn encourage all pregnant ppl in the UK to get their booster when they are offered it... 1/… The JCVI advises that the booster vaccine dose should be off If you are in the USA and pregnant or recently pregnant, you will be offered a booster vaccine as soon as you are six months out from dose 2. And @acog recommends you get it. 2/… Text from new ACOG guidance. ACOG recommends that pregnant a
Nov 15, 2021 16 tweets 6 min read
Wondering if #COVID19 #vaccination affects #periods? 💉🩸🤔

So was I!

Preliminary results from my study on this are out today in preprint... 🧵… To answer this question, we recruited two cohorts.

Cohort 1 consists of 250 people recruited before they received their COVID vaccine, who are keeping a record of their periods before and after vaccination. 2/
Nov 3, 2021 10 tweets 4 min read
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… 🧵 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/…
Oct 21, 2021 13 tweets 3 min read
Stressful times (war, famine) are associated with people experiencing more anovulatory and abnormal menstrual cycles.

But what about the pandemic? This paper used data from 18,076 ppl tracking their cycles with @NaturalCycles app to investigate… 🧵… The authors looked at user data entered from March - September 2019 (pre-pandemic) compared to March - September 2020 (Pandemic). They also asked users to rate their stress levels (retrospectively) in the pre-pandemic and pandemic periods. 2/
Oct 17, 2021 18 tweets 6 min read
Are you #breastfeeding? Thinking about whether to get the #COVID19 #vaccine?


This is a thread for you!

🧵... People who are breastfeeding can sometimes get forgotten in the focus on pregnancy. But your questions matter too! And I particularly want to make space to address those questions because a lot of people have contacted me, worried about one particular blog post... 2/
Oct 14, 2021 7 tweets 4 min read
Wondering if antibodies raised against #COVID19 #vaccines can bind to the placental protein syncytin-1 and harm #fertility?


Out yesterday! More data that addresses this question!

Spoiler alert: they don’t... 🧵… But why would anyone even think that such a thing might happen? Is it even worth researching?

The rumours that COVID19 vaccines would impact fertility were started by a vaccine skeptic who proposed that this might occur, so this is something that a lot of ppl may have heard. 2/
Oct 12, 2021 12 tweets 4 min read
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/
Sep 28, 2021 9 tweets 4 min read
Let's take a look at the data from the @CDCgov ACIP meeting last week on #COVID19 #vaccine safety in #pregnancy.

It continues to be reassuring!

First, let's take a look at the new data from the V-safe pregnancy registry... 🧵… As of the 13th September, the registry contained 5096 participants. 2/ Among 5096 people in the re...
Sep 8, 2021 6 tweets 2 min read
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/… 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/…
Aug 17, 2021 7 tweets 5 min read
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/…
Aug 13, 2021 11 tweets 4 min read
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/…