Three Things Thursday

What you need to know about Pfizer's bivalent vaccine & the "safety signal"

Jan 19, 2023

Three Things Thursday highlights three things I am paying attention to as an epidemiologist each week.1

Hoping these posts help to educate and empower you
to be healthy and create healthy communities.

Today’s Three Things Thursday focuses on the announcement from the Centers for Disease Control and Prevention (CDC) that one of the vaccine safety monitoring systems picked up a “safety signal” POSSIBLY linking Pfizer’s bivalent COVID-19 vaccine with an increased risk of stroke in individuals 65 and older.

Here is what you need to know —

First and most importantly, despite nonstop news coverage and SO MUCH misinformation online, there is —

No change in vaccination practice is recommended. CDC continues to recommend that everyone ages 6 months of age and older stay up-to-date with COVID-19 vaccination; this includes individuals who are currently eligible to receive an updated (bivalent) vaccine. Staying up-to-date with vaccines is the most effective tool we have for reducing death, hospitalization, and severe disease from COVID-19.

So — (second thing) here’s what happened…

Last Friday (Jan 13th) one of the surveillance systems that is tracking vaccine safety, the Vaccine Safety Datalink, picked up a “safety signal.” Think of this safety signal as your smoke detector telling you the battery is low. It is an automatic alert/signal that you need to take some action and replace those batteries.

I don’t know about you, but my smoke detectors used to chirp, and now they actually talk to me; telling me (in a really creepy voice that almost always starts talking at 2 in the morning) “low battery.” The chirp or creepy announcement always catches me off-guard and I never have new batteries when it goes off. But it is my smoke detector’s way of alerting me that there could be a problem (the batteries could run out and not be able to detect smoke) and that further action (replacing the batteries) is needed.

The chirp/creepy voice is a safety signal. It is calling my attention to something that may happen (battery fails) and that I need to take some action.

That’s what happened with the Vaccine Safety Datalink. The equivalent of the low battery chirp was triggered (through some automated statistical analysis). There was an accumulation of reports of stroke in adults 65 and older who had received their bivalent Pfizer booster. The safety signal/chirp got everyone’s attention and a rapid review of the data (i.e., action) was conducted.

In a rush to be transparent with the public about the safety signal (in the midst of a surprise, I’m assuming), CDC and FDA issued a press release acknowledging what had happened.

While I applaud CDC’s effort to get information out to the public quickly, the press release was sloppy. What was shared publicly was not (in my opinion) written for a general audience. It used vocabulary and made assumptions that are known to epidemiologists; not the general public. It lacked links to five pieces of data that were used to explain why (despite the safety signal being triggered) there is “no change in vaccination practice.”

The press release left me as an epidemiologist uncomfortable and disappointed because data was not shared (nor were the links to the studies they were basing their recommendations on) and it was not written for the public. Using an online tool, I found that the press release was written at a greater than 12th-grade reading level; all health information (especially something as concerning and controversial as this) should be written at a 7th-grade level (that’s a best practice).

How the information was communicated to the public opened the doors for increased questions, distrust, and misinformation.

Not only was the safety signal tripped, but now misinformation is spreading and distrust is growing. And for those of us who understand what the CDC meant by confounders, the totality of data, and statistical significance — I think we’re just sad. And I know that the work to increase vaccine uptake, slow the spread of infectious disease, and help individuals think about health as something we share (vs. individual freedom or choice) is going to be harder today than it was on January 12th.

While the intention of the press release was on point, the execution of it was not.

This makes me sad.

And it reminds me how important it is to communicate clearly and speak to your audience in a way that they will understand.

Third, here’s what you need to know —

The safety signal that was tripped connected the Pfizer booster to stroke in individuals 65 and older. Tipping the safety signal is equivalent to your smoke detector chirping. It says to take action now — investigate what is going on to ensure safety in the future.
Investigations of the data from all of the vaccine safety systems are ongoing. Data will be shared and discussed next Thursday, January 26 during an FDA Vaccines and Related Biological Products Advisory Committee (VRBPAC) meeting. You can watch the meeting live (I will) at this link. The meeting is scheduled from 8:30 am-5:30 pm ET.
We will know more after next week’s VRBPAC meeting. We will have data and (hopefully) clarity regarding what happened, why, and how it was determined that this was just a tripping of a system, not cause for concern.
COVID vaccines, especially the bivalent booster, are keeping people from developing severe disease, being hospitalized, and dying.
The Moderna booster is more effective than Pfizer.
The safety signal that was tripped only involved the Pfizer vaccine.
I would recommend getting the Moderna booster.

So stay tuned. Be sure you are subscribed so you can get my VRBPAC meeting summary next week.

And if you have questions, please let me know. The announcement of the safety signal trip was confusing, frustrating, and concerning, and it sparked questions and a lot of misinformation. What do you need to know?

Epi(demiology) Matters

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