2023-10-12 19:57:16
MONTREAL — Women are more likely than men to experience an adverse side effect following being vaccinated once morest the flu, confirms a meta-analysis led by a Montreal researcher.
These side effects range from a reaction at the site of the injection to a more serious systemic reaction that can impact daily life ― such as fever, headache, or body and muscle aches ― within seven days following influenza vaccination.
“Women may have a greater rise in antibodies following vaccination, so this may be associated with better protection,” said the study’s lead author, researcher Marilou Kiely, of the University of Montreal and the National Institute of Public Health of Quebec (INSPQ).
“A greater inflammatory response may be associated with injection site reactions or systemic reactions following vaccination.”
The difference between men and women is likely multifactorial, Kiely added. Genetic or hormonal factors may, for example, be involved. Certain reactions are more frequent following puberty and before menopause, which would be compatible with an influence of hormones, but we still see more frequent reactions in older women, she added.
We also know that women are more likely than men to seek medical help if they experience these side effects, which might have the effect of distorting the data we have a little, said Ms. Kiely.
Researchers from the University of Montreal, McGill University, Sainte-Justine Hospital, the INSPQ and their colleagues from Alberta and British Columbia combed through 18 studies bringing together a few more than 34,300 topics.
Their data shows an increased absolute risk of 115 additional cases of injection site reactions in women compared to men per 1,000 people vaccinated, and 74 additional cases of systemic reactions in women per 1,000 people vaccinated.
The risk of adverse side effects was higher in both younger and older women.
We already knew that the reaction of men and women can be different following vaccination. This new analysis, however, refines and clarifies the knowledge we have on this subject, explained Ms. Kiely, in particular by stratifying the data for men and women.
In particular, the researchers obtained data directly from the pharmaceutical companies that produce the vaccines, which allowed for a more in-depth analysis.
This study is published at a time when the seasonal flu vaccination campaign is in full swing, but also at a time when resistance to vaccination and conspiracy theories are popular in certain circles.
“It is well known that concerns regarding vaccination safety can lead to more vaccine hesitancy,” admitted Ms. Kiely. But it is better to be transparent and pass on the information. Even if women are more at risk of having these events following vaccination, these are mild events and will resolve quickly.”
The increase in these reactions may also be associated with a better response to vaccination, and it is therefore “plausible” that women are better protected following being vaccinated, she added.
“It is certain that in the short term this can increase concern, but we must reassure women and transmit the information that yes, we have observed a higher risk, but that these are symptoms which are mild and have no long-term impact,” Ms. Kiely said.
The findings of this meta-analysis were published by the Journal of Epidemiology and Community Health.
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