A study from Yale has found specific gene "signatures" that correlate with an effective response to the flu vaccine. The new research pinpointed specific clusters of genes that seem to be related to vaccine efficacy, but strangely discovered that while they could be associated with an above average response to the flu vaccine in those younger than 35 years-old, the exact opposite trend was found in those over the age of 60.

The new study included data from six separate influenza vaccination cohorts, comprising more than 500 subjects, and divided into two age groups: under 35 years or over 60. The team determined the efficacy of the flu vaccine by calculating the magnitude of the antibody response in each subject.

Further genetic analysis of the younger subjects identified nine genes with increased expression and six genes with reduced expression that indicated a high antibody response to the vaccine. In the older group there were no genes identified that were significantly different between those high and low vaccine responders.

The most fascinating aspect of the research was the discovery that the gene expression seen to heighten vaccine response in the young did not improve responses in those over the age of 60. Instead those older subjects with the same genetic characteristics were in fact worse off in their vaccine responses.

"Surprisingly, we found that baseline differences, both at the gene and module level, were inversely correlated between young and older participants," sats Steven Kleinstein, associate professor of pathology at Yale School of Medicine.

The strange inverse correlation between young and old subjects was a surprising anomaly that the researchers currently cannot explain. The team specifically note in the study that more research into these age differences will be important.

Ultimately this research will help improve vaccines and allow doctors to predict vaccine response in individuals. The new revelations also offer an insight into the genetic origins behind our immune system response.

The study was published in the journal Science Immunology.