Flu Shot Less Effective in Seniors — Here's Why

Flu vaccine responsiveness linked to molecular pathways in elderly patients

(RxWiki News) Flu vaccines are known to be less effective in the elderly. But until now, the mechanisms behind this phenomenon were not well-understood.

In a new study, researchers from the University of California (UC) and Emory University (EU) found that the baseline state of elderly patients' immune systems may be behind this reduced responsiveness to vaccination.

"By providing a more complete picture of how the immune system responds to vaccination, our findings may help guide the development of next-generation vaccines that offer long-lasting immunity and better protection of at-risk populations," wrote study author Shankar Subramaniam, PhD, a professor of bioengineering at UC, and colleagues.

Flu vaccines work by encouraging the production of antibodies (proteins that help the immune system identify viruses) in the body. Aging lowers the body's ability to have a good immune response after getting vaccinated — putting the elderly at a greater risk of severe flu-related complications.

To find out why this happens, Dr. Subramaniam and team vaccinated 212 patients across five flu seasons between 2007 and 2011. Around 50 of these patients were elderly.

They then used blood samples to identify the molecular pathways tied to immune responses in these patients. Previously published data on 218 additional patients was also included in this analysis.

Within one week of vaccination, the younger patients showed high levels of antibody-producing B cells. By comparison, the elderly patients showed high levels of cells called monocytes, which elicit inflammatory responses in the body.

These age-related differences were able to predict whether a vaccine would provide adequate flu protection with up to 80 percent accuracy.

Dr. Subramaniam and colleagues said that reducing inflammatory responses in elderly patients after vaccination could potentially provide better protection against the flu. However, more research is still needed.

Fluzone High-Dose is a flu vaccine designed specifically for patients age 65 and older. This vaccine helps older patients develop better immune responses.

A separate study published in the New England Journal of Medicine found that elderly patients who received a high-dose vaccine were about 24 percent less likely to be diagnosed with the flu than patients who received a standard vaccine.

The current study was published Dec. 15 in the journal Immunity.

The National Institutes of Health and the National Science Foundation funded this research. The authors disclosed no conflicts of interest.

Review Date: 
December 14, 2015