Testosterone cuts flu vaccine's effectiveness among men

Researchers have identified a link between certain genes affected by testosterone and antibody responses to an influenza vaccine.

The study, led by researchers at Stanford University, suggests that testosterone levels may partially explain why men often have weaker responses to vaccines than women.

Previous research has shown that men typically experience more severe viral and other microbial infections than women, who tend to mount stronger immune responses to infections and vaccinations.

In the new study, researchers analyzed the antibody responses of 53 women and 34 men of various ages to the 2008-2009 seasonal influenza vaccine.

Compared to the men, the women produced antibodies that in laboratory tests could more effectively neutralize the influenza virus.

To explain this difference, the scientists searched for patterns in gene expression, or the degree to which specific genes are turned on or off. They found that men with weak vaccine responses tended to have high expression levels of a certain cluster of genes involved in the metabolism of lipids (fats).

The researchers found that men with high levels of testosterone and elevated expression of the gene cluster had weaker antibody responses to the vaccine than women and men with low testosterone.

These results suggest that testosterone may suppress immune responses to vaccines by altering expression patterns of specific genes, but further research is needed to determine the mechanism.

The findings have been published in Proceedings of the National Academy of Sciences.