Why the Flu Vaccine is Less Effective at Protecting the Elderly

Why is the flu vaccine less effective at protecting older individuals? That's a good question and now, a new study may have found the answer.

"We provide novel evidence of a potential connection between the baseline state of the immune system in the elderly and reduced responsiveness to vaccination," said Shankar Subramaniam, one of the researchers, in a news release. "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 production of at-risk populations."

Flu vaccines contain proteins that are found in circulating viral strains, and offer protection by eliciting the production of antibodies, which are proteins that help the immune system identify pathogens and protect against infectious disease. However, vaccination is less effective in the elderly. Why this was was unknown until now.

The researchers first identified molecular signatures of immunity to flu vaccination using systems biology approaches, which involve the computational and mathematical modeling of complex biological systems. They vaccinated 212 subjects, including 54 elderly individuals, across five influenza vaccine seasons. Then, the scientists analyzed the blood samples for the subjects.

Within one week of vaccination, young individuals showed high levels of antibody-producing B cells. The elderly, instead, showed high levels of immune cells called monocytes, which elicit inflammatory responses in the body. These age-related differences predicted impaired vaccine-induced immune responses observed in the elderly three weeks later.

"This supports the concept that inflammatory responses at baseline may be detrimental to the induction of vaccine-induced antibody responses," said Subramaniam. "While it is early to suggest, supplementary therapeutic approaches, such as reducing the inflammatory response in elderly patients after vaccination, would be valuable avenues to pursue. However, this warrants longer and more detailed investigations."

The findings are published in the journal Immunity.

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