Women report more vaccine troubles
Reports of COVID-19 vaccine side effects support what many have anecdotally observed: women shoulder the bigger burden.
Of nearly 7,000 reports processed through the Centers for Disease Control and Prevention’s Vaccine Adverse Event Reporting System from Dec. 14 to Jan. 13, more than 79% came from women. The most frequently reported side effects were headache, fatigue and dizziness.
Women also are more likely than men to experience some of the vaccine’s more unusual side effects, such as an itchy red rash that appears at the injection site commonly known as COVID arm or Moderna arm, as about 95% of the reactions occur with the Moderna vaccine. Overall, women account for 77% of the Moderna vaccine’s reported side effects.
These side effects – even if unusual – are a good sign the vaccine is working to arm the body’s immune system against the coronavirus. But why are women more likely to experience them than men?
Health experts said it might be from biological differences, inconsistent reporting by men and gender bias in clinical trials.
Women exhibit a greater immune response to vaccines than men, experts said, which might partially explain why more of them have reported side effects to the COVID-19 vaccine.
“From a biological perspective, women and girls produce sometimes twice as many infection fighting antibodies from vaccines,” said Rosemary Morgan, a research scientist at Johns Hopkins Bloomberg School of Public Health.
Although there’s no data comparing men and women’s immune response to the COVID-19 vaccine, researchers from a 2019 study found women developed greater cytokine and antibody responses compared to men after getting the flu vaccine.
This could be from women having a higher frequency of CD4+ T cells, also called “T helper cells,” which activate other cells from the immune system that make antibodies to fight the virus, said Dr. Daniel Saban, an immunologist scientist at Duke University School of Medicine.
Hormones also could dictate the different immune responses between men and women, Saban said, as some immune cells have estrogen receptors on them.
Women produce more estrogen than men, which might impact how the immune cells work.
Also, men might be reporting side effects less frequently, health experts said.
Clinical research has historically neglected sex differences, Morgan said, which has affected how women respond to approved vaccines and medications.
Women were mostly excluded from clinical trials until the 1993 National Institutes of Health Revitalization Act was passed to ensure the inclusion of minorities in clinical research.
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