COVID vaccination causes short-lived increases to menstrual cycle length in some people. But how?

A new paper has come out that examines the possibility that this occurs via a direct effect on the ovaries. But does it show that?

(TLDR: Not really...) 🧵

nature.com/articles/s4154… I'll start by saying that this isn't the first mechanism I would investigate myself. As the authors acknowledge, other vaccines - notably COVID vaccines that do not leave the site of injection - have the same effect. This suggests an effect mediated by the immune response. 2/

67 studies including 723,988 ppl who received a #CovidVaccine during #pregnancy!

😷 61% less likely to be infected

🏥 94% less likely to be hospitalised

🤰🏻 12% less likely to have a hypertensive disorder and 9% less likely to have a C section

1/

gh.bmj.com/content/9/4/e0… 👶🏻 Babies 8% less likely to be admitted to NICU

👍🏾 No increased risk of any adverse outcomes in pregnancy or to babies.

2/

Studies looking for evidence that mRNA COVID vaccines cross the placenta have not found it (192 babies).

A case report finds degraded vaccine mRNA in umbilical cord blood from one baby, born 2d after their mother was vaccinated.

What does this mean? 🧵

ajog.org/article/S0002-… mRNA degrades quickly, so it’s possible we haven't detected vaccine mRNA in the placenta because we didn’t look quickly enough.

To address this, the authors look at placentas for two babies born two and ten days after their mothers received a dose of COVID vaccine. 2/

🇨🇦 85,650 babies born after #CovidVaccination in #pregnancy vs 56,336 babies from unvaccinated pregnancies

👉🏻 Risk of death and disease lower in newborns from vaccinated pregnancies

👉🏻 No difference in hospital admission up to six months old

1/

jamanetwork.com/journals/jamap…
This was designed as a safety study and the results are reassuring.

This is unsurprising, given the very extensive evidence we already have on the safety of mRNA COVID vaccines in pregnancy. 2/

docs.google.com/document/d/19F…

👩🏿‍🔬 RCT of Pfizer #CovidVaccine given at 24-34 weeks of #pregnancy, with babies followed to six months old.

🤰🏽 173 vaccinated vs 173 saline control

🏥 No difference in rate of severe AEs

👶🏼 No difference in babies' health at birth or up to 6 months

🧵

classic.clinicaltrials.gov/ct2/history/NC… This came out while I was away last month, so I didn't post about it at the time. But I talk about it on @SkepticJonGuy's video released last night, which prompted me to share a few (belated!) thoughts... 2/

x.com/SkepticJonGuy/…

🇺🇸 Yesterday, the FDA approved an RSV vaccine for use in pregnancy.

There was a non-significant difference in preterm birth in the trial, which patients will be informed about.

Let's look at the minutes of the meeting to understand these decisions... 🧵

fda.gov/news-events/pr… Before we start, here are links to the trial report...



And the meeting minutes... 2/

nejm.org/doi/10.1056/NE…
fda.gov/media/169361/d…

@davidicke Hi David. Independently-generated data looking at safety of COVID vaccines in more than 360,000 people vaccinated in pregnancy find no increased risk of any pregnancy problems.

How do we reconcile that with the spontaneous reporting in your video?... 🧵

docs.google.com/document/d/19F… @davidicke First, for context... it would probably help you to realise that those 458 spontaneous reports were out of approximately 48,000 people who had been vaccinated in pregnancy at that time. 2/

nejm.org/doi/full/10.10…

jamanetwork.com/journals/jama/…

@MarkWar16520311 To understand adverse effects of vaccines, it helps to think about the phases of the immune response. First, we have the innate response, which we might think of (roughly) as being inflammation. This lasts from minutes after vaccination to 48 hours-ish. 1/ @MarkWar16520311 Most adverse events happen in this timeframe and whenever we see inflammation-type symptoms (sore arm, fever, myocarditis), we should straight away be thinking: that might be the vaccine. 2/

@drdrew @DailyClout @naomirwolf @DrKellyVictory @AskDrDrew Hi again Naomi! @naomirwolf

You say I couldn’t point you to any peer-reviewed evidence on the safety of COVID vaccines in pregnancy. It was linked in my first tweet, here… 1/

https://twitter.com/VikiLovesFACS/status/1647498824414384129?s=20

@drdrew @DailyClout @naomirwolf @DrKellyVictory @AskDrDrew Maybe you didn’t spot the studies, since you have to click through to get to the list? So I’ll post links individually here.

You might see why I prefer to point people to a master document…

2/

nejm.org/doi/full/10.10…

nejm.org/doi/full/10.10…

jamanetwork.com/journals/jama/…

@toadmeister Hi Toby! We’ve discussed before how data from hundreds of thousands of humans shows no increased risk of pregnancy loss or congenital abnormalities following COVID vaccination in pregnancy.

But since you’re keen, let’s talk about the rodent data… 1/

docs.google.com/document/d/19F… @toadmeister It’s not true that these data were recently released as a result of an FOI request. Pfizer went out of their way to get them published following peer review, and they’ve been freely available since the summer of 2021, here… 2/

ncbi.nlm.nih.gov/pmc/articles/P…

#Menstrual changes in those who received a #CovidVaccine (3,635), caught #COVID (1,802), both (1,354) or neither (5,788)...

🦠 Infected more likely to report shorter cycles, missed periods, heavier periods, spotting

💉Vaccinated only: no difference

1/

cell.com/iscience/pdf/S… Previous studies have found menstrual changes associated with vaccination, but these have been small and short-lived, so it's perhaps not surprising that a retrospective survey design can't detect them. 2/

https://twitter.com/VikiLovesFACS/status/1593340088955568131?s=20

🇮🇱 48,868 babies followed for first 120 days of life. Does being born after a #CovidVaccine booster in #pregnancy protect against hospitalisation for COVID?

👉🏻 Yes! With 53% effectiveness compared to two doses only.

1/

nature.com/articles/s4159… Other important findings…

👉🏻 Protection is greater when the booster dose is given later in pregnancy

👉🏻 Protection wanes as babies get older, with no significant protection after 90 days, in this study.

2/

🇺🇸 30,311 babies followed from birth to 6 months, of whom 10,893 were born following #CovidVaccination in #pregnancy.

👉🏻 Protection against COVID infection in the delta period was 56%

👉🏻 In the omicron period, 13%

1/

nature.com/articles/s4146… This study quite nicely shows how protection declines over time as maternal antibodies wane. For delta, protection against infection is:

84% in the first two months

62% in the first four months

56% in the first six months

2/2

@toadmeister Hi Toby! Our most up to date information on births and newly registered pregnancies in the NHS (to October 2022) shows no decline in either... 1/

https://twitter.com/VikiLovesFACS/status/1624066711405187074?s=20

@toadmeister It’s worth noting that the HES dataset, which you’re using there, isn’t yet finalised (though it will be shortly). So some births in the most recent months are not yet included in the dataset… but that doesn’t mean they didn’t happen. 2/

https://twitter.com/VikiLovesFACS/status/1590976113295167491?s=20

@DrAseemMalhotra Hi Aseem! It would be very surprising if this one study had really found what the author claims, given the overwhelming body of evidence now showing no increased risk of any pregnancy problems following COVID vaccination... 1/

https://twitter.com/VikiLovesFACS/status/1628369116967870464?s=20

@DrAseemMalhotra But the study he is talking about has been preprinted, so we can take a look right now... 2/

preprints.org/manuscript/202…

@DarrellSpins That’s a good question. For increased cycle length, we can make two observations:

1. People on combined hormonal contraception are less likely to experience this

1/

frontiersin.org/articles/10.33…

medrxiv.org/content/10.110… @DarrellSpins 2. People vaccinated early in their cycle are more likely to notice an effect.

2/

medrxiv.org/content/10.110…

Just out! A new meta-analysis of 81,349 ppl receiving #CovidVaccine during #pregnancy compared to 255,346 unvaccinated. Vaccination...

👉🏻 Protects against infection

👉🏻 Lowers chance of stillbirth by 27%

👉🏻 Lowers chance of babies needing NICU by 12%

jamanetwork.com/journals/jamap… I’ve been asked for some additional context around whether the 27% reduction in stillbirth reported by this paper is likely to be an overestimate…

🧵

https://twitter.com/hicksyalex/status/1577536665240870912

19,622 ppl tracking #periods, of whom 14,936 receive #CovidVaccine

👉🏻 Dose 1 associated with a 0.7d delay to the next period

👉🏻 Dose 2: 0.6d delay

👉🏻 2x doses in one cycle: 3.91d delay

👉🏻 Back to normal next cycle

👉🏻No change to period length

🧵…

bmjmedicine.bmj.com/content/1/1/e0… We see these effects with all types of COVID vaccine (mRNA, adenovirus, inactivated virus), suggesting this is likely to be a result of the innate immune response – akin to side effects such as sore arm and fatigue – rather than an effect of any particular vaccine component. 2/

This study looked at #breastmilk after #CovidVaccination in 11 people.

👉🏻 mRNA detectable in whole milk of 3 of them

👉🏻 Maximum concentration 0.1 parts per billion

👉🏻 This is roughly equivalent to a single tear in an Olympic pool

1/

jamanetwork.com/journals/jamap… The findings are roughly in line with two previous studies which concentrated breast milk in order to detect very low quantities of vaccine mRNA (in fact, this one finds a little less). Low et al... 2/

https://twitter.com/VikiLovesFACS/status/1410147655737544707?s=20&t=BHNUqGrWIFRCIubwXztP3w

@NoMaloneZone @qandamazon I’ve read it so you don’t have to! (Though read it. It’s short, at least.)

We begin by noting that vaccines save lives – true. We go on to discuss the author going on breakfast television – also true (I understand) but not normally the stuff of the scientific literature. 1/ @NoMaloneZone @qandamazon The author then talks about the death of his 73-year-old father from coronary artery disease. I’m sorry for his loss. 2/

@jneill @1goodtern @ClareRayner6 I’ll start with stillbirth since the evidence there is very clear. Sadly COVID infection in pregnancy does increase the risk of stillbirth by about 2.5-fold… 1/

nature.com/articles/s4157… @jneill @1goodtern @ClareRayner6 And our national statistics did bear this out, in that we saw increased stillbirths in England and Wales at the height of the pandemic… 2/

ons.gov.uk/peoplepopulati…