Why Women Experience Worse COVID-19 Vaccine Side Effects Than Men

Ever since news of a COVID-19 vaccine was first announced, much of the world breathed a sigh of relief as the scientific breakthrough signalled a possible return to normalcy. However, the discourse surrounding any potential side effects of the vaccines also began to surge, and in a study published in February 2021, it emerged that women are more likely to experience worse COVID-19 vaccine side effects than men, (via The New York Times). 

In the study, the Centers for Disease Control and Prevention analyzed the first 13.7 million COVID-19 vaccine doses administered in the United States. The data concluded that 79.1% of all reported side effects came from women, despite the fact only 61.2% of the vaccine doses had been given to women at the time. 

The CDC researchers also reported that individuals who had experienced rare anaphylactic reactions to the Moderna COVID-19 vaccine were female, and 44 of the 47 people who had anaphylactic reactions to the Pfizer vaccine were also women, (via JAMA Network).

Should women be worried about an increased risk of side effects?

Commenting on the recent findings, microbiologist and immunologist at the Johns Hopkins Bloomberg School of Public Health, Sabra Klein, said she is "not at all surprised" by the results of the study as "this sex difference is completely consistent with past reports of other vaccines," (via The New York Times). 

Dr. Klein is referring to previous studies that have displayed similar results to the COVID-19 vaccine findings relating to women, including a 2013 study that concluded women between the ages of 20 and 59 were four times more likely to experience allergic reactions after receiving the 2009 pandemic flu vaccine, (via Science Direct).

However, despite being more likely to develop side effects with some vaccines, any reactions tend to be mild, and side effects can often signify that the vaccine is doing its job. Dr. Klein added, "You are mounting a very robust immune response, and you will likely be protected as a result."