STANFORD, Calif. (CBS Sacramento) – Men typically experience more severe infections after a vaccination than women.

And researchers at Stanford University think they may have discovered why.

Their study found a link between certain genes that are affected by testosterone and antibody responses to a flu vaccine.

The scientists analyzed how antibodies responded to the 2008-2009 influenze vaccine in 53 women and 34 men of different ages.

In lab tests, the women produced antibodies that did a better job of neutralizing the flu virus.

To explain this difference, the scientists looked for the different ways the genes were turning on and off.

They found that in men with weak responses, those same genes were involved in the production of certain fats in the body.

And the men with the weakest responses showed a higher level of testosterone.

Women and men with lower levels of testosterone had a better response to the vaccine.

Previous studies have suggested that testosterone may regulate many of these same genes, reports

The findings are published in Proceedings of the National Academy of Sciences.