The flu vaccine causes more adverse effects in women

New research examining the results of 18 clinical trials involving 34,343 adults has found that flu vaccine It does not produce the same side effects in women as in men and, in fact, they are more common in women, especially those over 65 years of age. Specifically, women are 43% more likely to suffer discomfort in the arms – pain or swelling –and 27% more likely to experience systemic reactions, such as fever, muscle pain or headache.

The researchers, led by Dr. Marilou Kiely at the University of Montreal, found that women who were under 65 years of age were also more likely to experience side effects after flu vaccination, including population groups for which receiving this vaccine is indicated. such as young women with health problems and pregnant women.

The results have been published in Journal of Epidemiology & Community Health and reveal that there is a higher risk of reactions to the flu vaccine for women compared to men, “regardless of age and type of vaccine. Transparent communication of this risk could increase vaccine confidence and limit vaccine hesitancy. Future studies should report results stratified by sex and explore the role of gender in the occurrence of adverse events,” the researchers stated in the article.

The benefits of the flu vaccine outweigh the risks

The results of the study indicate that arm pain is the most common side effect after receiving the flu vaccine, and that muscle aches and headaches are the most common reactions throughout the body, although women are more likely to experience these whole body reactions is relatively small because It only affects 74 more women for every 1,000 people vaccinated.

“Most of the symptoms described associated with vaccination [contra la gripe] “They are mild symptoms.”

In women over 65 years of age, the probability of suffering more serious arm problems that temporarily prevent them from carrying out daily tasks is 51% greater than in men and they are also 48% more likely to present serious reactions in whole body, such as muscle aches and fever, that affect your daily routines. The difference in the serious reactions throughout the body among women and men is lower in those over 65 years of age compared to younger people, suggesting that the immune system of older women responds less intensely to the flu vaccine.

However, and as the authors explain in statements published in SMC Spain, “the data suggest that most reactions are mild, self-limited and rarely serious,” so it is important to take into account the potential benefits of the flu vaccine. in older people and patients with certain diseases, who are considered vulnerable groups especially protected by vaccination against respiratory infection.

Stanislao Nistal, virologist and professor of Microbiology at the CEU San Pablo University, also speaking to SMC Spain, pointed out that “most of the symptoms described associated with vaccination are mild symptoms.” This expert explains that “the study uses the expression “risk of adverse effects” to name something called reactogenicity of a vaccine (reactions associated with vaccine inoculation). “Reactogenicity is related to the activation of the patient’s immune system to fight the virus, which is generally mild and transient, so using the expression risk of adverse effects has a connotation that does not encompass the complexity of what is happening.”

“Among the symptoms that the study calls severe grade 3 symptoms, such as ecchymosis, hardening, swelling at the injection site or erythema, all are transient and reversible symptoms and can be attenuated with treatments. The number of patients within the risk group with severe symptoms is also very low.”

And he adds that “along with the analysis of what the article calls the risks of symptoms of whatever type, correct information must be accompanied by a fundamental value in any vaccine, the risk/reward ratioespecially in patients at risk of developing complications associated with the flu, which in the study would be those over 65 years of age.”

“The data provided by the study about the greater reactogenicity in women is interesting. It is not new, but it does affect the possibility of defining parameters that would serve to ensure that the reactogenicity of the vaccine in women is not so intense, although the degree of immunization and reaction that may accompany it and that may be necessary in men or women is unknown. in women to have optimal protection against the virus.” “It would be convenient to clarify some expressions and add some additional data to the study that talks about the safety and effectiveness of vaccines in the context of the reactions they produce,” concludes Nistal.


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