World Views | Blood clots aren’t the only vaccine side effects worth studying

Faye Flam, MDT/Bloomberg

One can hardly blame people for being worried about the new Covid-19 vaccines when there are so many anecdotal reports of weird side effects — including women experiencing disturbing changes in their menstrual cycles.
Reports of early and unusually heavy periods or other irregularities were becoming so common earlier this spring that University of Illinois anthropologist Kate Clancy started collecting them. People may wonder, rightly, why this isn’t being studied in a more systematic way. If something this unexpected can happen, then what else?
The original clinical trials were set up to get the minimum information needed to win emergency use approval, and follow-up study has been less than systematic. Yet getting a handle on these disturbing side effects wouldn’t be that hard. Several doctors I talked to mentioned there’s a self-reporting system called V-Safe, but they’d like to see something bigger and more systematic, where people tracked all sorts of physical changes in real time, including these peculiar menstrual irregularities.
There’s ample evidence that sex differences matter in responses to the vaccine and need more study. Women are more likely to report mild or moderate side effects, and much more likely to suffer the severe ones.
Twenty-two of the 28 people who suffered blood clots possibly associated with the Johnson & Johnson vaccine were women. Women also make up nearly all of the small number who had a severe allergic reaction — anaphylaxis — following injection with other vaccines. Women are also much more likely to suffer severe, extensive rashes after getting the Covid-19 vaccine — another uncommon but troubling side effect.
As I learned researching this column on Covid vaccination during pregnancy, women and men often react differently to infectious agents and vaccines because women’s immune systems are adapted to protect a fetus from infection but also not to attack the foreign cells that make up the fetus.
It’s not surprising that sex hormones and the immune system can influence each other, says Johns Hopkins University immunologist Sabra Klein. She said she’s submitted a proposal to the National Institutes of Health to study the menstrual problems. I asked her whether there’s any understanding of whether the other side effects are more common only in women of reproductive age, or across all age groups. She said that hasn’t been studied yet, but should be.
All the women who had blood clots following the Johnson & Johnson shot were between 18 and 48. Doctors are still discussing whether women of reproductive age should be advised to avoid it in favor of the other approved vaccines, but nobody, she says, is doing studies on the question.
Some people have tried to dismiss the blood clot problem by noting that birth control pills are also associated with blood clot risk. But neither problem should be dismissed. More work should be done to prevent women from getting blood clots associated with birth control pills too.
Right now, the main source of public information on vaccine side effects is a website called the Vaccine Adverse Events Reporting System (VAERS).
The right reason to be confident in vaccines is that they provide impressive protection against a deadly virus…The wrong reason would be blind trust of public health officials or Big Pharma.
The public is worried because these vaccines are new. But new doesn’t have to mean poorly understood. Because these shots are being distributed to so many millions of people, it’s possible to collect huge amounts of safety and side effect data, as well as data identifying when and why a few people still get infected after vaccination.
That data will be useful as the world is likely to continue to update vaccines, and they are likely to be the most important part of the fight against this pandemic long into the future. Public trust is critical, but the CDC, the doctors and public health experts and could do more to earn it.
Faye Flam, MDT/Bloomberg
[Abridged]