Women have a stronger immune response than men when given the flu vaccine, new research shows.
This may mean that vaccinated women are better protected against catching the flu than vaccinated men, although the new study did not look at this directly, the researchers said.
In the study, researchers examined the inflammatory responses of 53 women and 34 men following vaccination with a flu shot.
Scientists found that men had a weaker response, or less inflammation in their bodies, than women after receiving the vaccine, and the response was weakest among some of the men who had the highest testosterone levels.
The finding "reinforces the message that there are major differences between men and women in terms of their immune systems," said study researcher Mark Davis, a professor of microbiology and immunology at the Stanford School of Medicine. "Like many other areas, it hasn't been that well explored."
Davis said the study does not make immediately clear whether men and women have different levels of flu protection after vaccination, but other research suggests they do. [6 Flu Vaccine Myths]
"There is a literature to say women have better responses in general to infectious diseases, including flu," Davis told LiveScience.
The reasons for the difference are not entirely known, but the researchers noted that testosterone suppresses inflammation.
It’s also possible there is a genetic component to people's flu responses, the researchers said. While the mechanism is not entirely clear, the researchers found the vaccine activated certain genes, and this activation predicted who would have the weakest flu shot response.