Thread by @ScienceUpFirst

A recent safety report by Pfizer has been seized upon by misinformers. There’s nothing particularly new or scary about it, despite the #Pfizer #VaccineSideEffects hashtags circulating online.

Let’s dig in on how this data has been misrepresented 👇

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#ScienceUpFirst

Part of the mix up comes from a misunderstanding of “adverse events”.

Adverse events (AEs) ≠ side effects

AEs may or may not be related to a treatment (e.g. vaccines) and they are monitored for both treatment groups and placebo groups.

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#ScienceUpFirst

For example, if a trial participant swallowed a penny, that would be included as an adverse event. Even though it’s clear vaccines can’t make you swallow pennies.

As always, correlation ≠ causation

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#ScienceUpFirst

There’s a scary claim that pg 30 (“Adverse Events of Special Interest” (AESI) appendix) is a list of side effects. It's not.

AESI are often specified *before* the trial begins as events to be on the lookout for and alerted to ASAP if they occur (1).

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Lists of adverse events like these are useful tools that can help signal possible related side effects (2).

But because this report uses voluntary data (and not data from everyone vaccinated), it’s missing the denominator / how common each AE is.

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#ScienceUpFirst

This data is from Feb 28, 2021 (more than a year ago!), so a bit out of date.

E.g. there's missing info about vaccines for children. At the time children were not eligible for vaccination. We now know COVID-19 vaccines are safe for kids 5+ (3, 4).

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#ScienceUpFirst

Instead of getting freaked out by the list of things Pfizer was watching for, read the Discussion section, which says:

“The data do not reveal any novel safety concerns or risks requiring label changes and support a favorable benefit risk profile...”

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#ScienceUpFirst

Health Canada collates all the data from the Pfizer report but for the Canadian pop: health-infobase.canada.ca/covid-19/vacci…

@ENirenberg taught us a lot about how this data is being misrepresented. Check this out for a deeper dive👇

https://twitter.com/ENirenberg/status/1498852915758485509?s=20&t=RjcsaxoEQqX7TGPB-guXGg

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Questions? Leave a reply below

References:
1: publichealthontario.ca/-/media/docume…
2: health-infobase.canada.ca/covid-19/vacci…
3: canada.ca/en/public-heal…
4: nejm.org/doi/full/10.10…

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