more women report vaccine side effects than men
safety data from the first wave of vaccinations show 80 per cent of those who reported side effects were women.
mar 9 2021
3 minute read
women experience more severe side effects from the covid-19 vaccine, than men. getty
as the first 13 million or so americans rolled up their sleeves to get vaccinated late last year, a trend quickly became clear: women are bearing the brunt of the side effects.
a new study , published by the centers for disease control and prevention last month, took a closer look at one month of safety data from the first wave of vaccinations that began on dec. 14. the results were glaring: of the just under 7,000 people who reported side effects to the cdc, almost 80 per cent of those were women, despite receiving 61.2 per cent of the vaccines.
shelly kendeffy, a 44-year-old medical technician from pennsylvania, didn’t have to wait long to confirm the findings after she received her second dose of the moderna vaccine. a sore arm quickly gave way to body aches and flu-like symptoms that lasted around 24 hours, according to the new york times . “my teeth were chattering, but i was sweating — like soaked, but frozen,” she said.
kendeffy polled her colleagues at work the next day and found that almost all seven of the women she spoke to had similar experiences, while the men, relatively speaking, got off easy. four of the eight had no symptoms at all and the remainder had mild pain, aches or a headache that would be a walk in the park compared to what kendeffy went through.
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“i work with some very tough women. clearly, us women suffered a severity of the side effects,” kendeffy said, adding she has no regrets and was quite happy to be vaccinated. “i wouldn’t change a thing, because it sure beats the alternative. but i also didn’t know what to expect.”
as it turns out, she shouldn’t have been all that surprised, according to sabra klein, a microbiologist and immunologist at the johns hopkins bloomberg school of public health. “this sex difference is completely consistent with past reports of other vaccines.”
indeed, a 2013 study found that four times as many women between the ages of 20 and 59 reported allergic reactions to the 2009 pandemic flu vaccine than men of the same age. another study, looking at a 26-year period of vaccination beginning in 1990, concluded women made up 80 per cent of the group that suffered an anaphylactic reaction to the medicine.
there are competing theories as to why women have more adverse reactions to vaccinations than men but a big part of it may be behavioural, said rosemary morgan, an international health researcher at the johns hopkins bloomberg school of public health. men are less likely to see a doctor when feeling ill and it follows, she said, that they might similarly downplay the effects of a shot in the arm.
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but there are also biological factors at play, as evidenced by the ways the immune systems of different genders respond to vaccination, said julianne gee, a medical officer in the cdc’s immunization safety office. in women, the immune system mounts a more aggressive response, often producing twice as many infection-fighting cells in response to some vaccines, including measles, hepatitis b and mumps and measles.
because this response is more robust in younger patients, gee said it may be tied to sex hormones that have an influence on the body’s immune cells. similarly, testosterone — which klein said can be “beautifully immunosuppressive” — may dampen the response seen in men.
dose size may also matter, with studies showing women tend to absorb and process drugs differently than men and may not need the same quantity to achieve immunity. factor in the fact that clinical trials prior to 1990 largely excluded women and you have a recipe for deviation across genders.
ultimately, the enhanced response some women experience after vaccination fades quickly and serves as evidence it is having the desired effect, klein said. it might be prudent, however, to better prepare them for the experience. “women have greater immunity, whether it’s to ourselves, whether it’s to a vaccine antigen, whether it’s to a virus,” klein said. “i think that there is value to preparing women that they may experience more adverse reactions.
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“that is normal, and likely reflective of their immune system working.”
dave yasvinski is a writer with healthing.ca
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