Why Men Have Weaker Responses to Vaccines Than Women: Testosterone to Blame?

Researchers have long known that men often have a weaker response to vaccines than women. Now, they may have found out why. Scientists have identified a link between certain genes affected by testosterone and antibody responses to an influenza vaccine.

Previous research has shown that men typically experience more severe viral and other microbial infections than women. Women, in contrast, tend to mount stronger immune responses to infections and vaccinations. Needless to say, it's important to understand exactly why this is in order to develop more effective treatments for both men and women.

In order to find out a bit more about immunities, the scientists analyzed the antibody responses of 53 women and 34 men of various ages to the 2008-2009 seasonal influenza vaccine. In the end, the researchers found that compared to the men, the women produced antibodies that could more effectively neutralize the influenza virus.

The scientists weren't done yet, though. In order to find out the reason behind this difference, the researchers searched for patterns in gene expression, or the degree to which specific genes are turned on or off. In the end, 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, which are fats. Previous studies have suggested that testosterone may regulate the expression of many of these genes. In fact, the scientists 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 findings are important for the future development of vaccines. More specifically, they show that testosterone may suppress immune responses to vaccines by altering expression patterns of specific genes. That said, future research is needed to determine exactly what the mechanism might be.

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