Home >Opinion >Columns >Gender-specific side effects of vaccines deserve to be studied

One can hardly blame people for being worried about the new covid 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 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 studies have been less than systematic. Yet, getting a handle on these side effects should not 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 severe ones. Twenty-two of the 28 people who suffered blood clots possibly associated with the Johnson & Johnson (J&J) vaccine were women. Women also make up nearly all of the small number who had a severe allergic reaction—anaphylaxis—after injection with other vaccines. Women are also much more likely to suffer severe, extensive rashes after a jab, another uncommon but troubling side effect.

As I learnt researching 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 foetus from infection, but also not to attack the foreign cells that make up the foetus. 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 menstrual problems. On 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 this hasn’t been studied yet, but should be.

All the women who had blood clots after the J&J shot were between 18 and 48. 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.

The main source of public information in the US on vaccine side effects is a website called the Vaccine Adverse Events Reporting System (VAERS). But its information can be misleading. With half the US population having got covid shots at this point, it’s inevitable that some will develop severe diseases and even die for reasons that have nothing to do with the vaccination campaign. On the other hand, VAERS is going to miss anything people don’t take the trouble of reporting, and most people will not have the time or knowledge or interest to do this.

The right reason to be confident of vaccines is that they provide impressive protection against a deadly virus, and that the materials they introduce into the body quickly degrade or get destroyed by the immune system. Unlike the virus itself, they can’t replicate themselves, and any side effects should wane quickly. The wrong reason would be blind trust of public health officials or Big Pharma.

A failure to systematically study vaccine side effects could contribute to vaccine scepticism—and while women have been quicker to get vaccinated, they are also more likely to express concern over side effects. And vaccine hesitancy is already causing trouble in American nursing homes, according to a recent story in the Boston Globe, revealing that a number of nursing home workers are refusing and some newer residents have not been able to obtain a vaccine.

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 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. This data will be useful as the world is likely to keep updating 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 officials, doctors and public health experts could do more to earn it.

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