The flu vaccine is more effective in women than in men, according to new research HealthDay reported.
Researchers found that men with higher levels of the testosterone are more likely to have weak or no response to the flu vaccine and they tend to suffer more when they have the bug, HealthDay reported.
"Men, typically, do worse than women in immune response to infection and vaccination," David Furman, Stanford research associate and lead study investigator, told HealthDay.
In a report released today in the Proceedings of the National Academy of Sciences, researchers suggest this is because the male hormone causes genes in the immune system to produce lower numbers of antibodies or defense mechanisms in response to the vaccine.
According to NBC News, not only does this study suggest mean that men don't "mount a strong defense" against the flu, it implies they have weaker immune systems than women and are more vulnerable to severe bacterial, viral and parasitic infections.
Furman told HealthDay that researchers also found that men's immune systems don't respond as well as women's to vaccinations against the yellow fever, hepatitis and many other diseases.
For their study, researchers studied a variety of immune system proteins and cells using complex systems to detect gene expression in the blood of 54 women and 37 men of different ages. Then they analyzed the blood the participants after they received flu shots and found that men, as a group, had a more muted response to the vaccine, NBC News reported.
"We found a set of genes in men that when activated caused a poor response to the vaccine, but were not involved in female response," Furman said. "Some of these genes are regulated by testosterone."
Testosterone is tied to classic male sexual characteristics, such as muscle strength, beard growth and risk-taking.
"This has a lot of implications for vaccine development," Furman said.
He told HealthDay vaccine responses in men could improve if they were given twice the dose or if their testosterone levels were reduced.
