A new Yale School of Medicine study has answered the question of why younger bodies respond better to flu vaccines than older ones.
Researchers found that healthy older adults produced protective antibodies for the flu vaccine at a different rate than younger adults. Lower vaccine responsiveness in older adults is related to less effective immune responses. The results represent the first genome-wide analysis of age-dependent responses to the flu vaccine. The study was published in the journal Aging on Jan. 14.
“The research was conducted with the hope that the genetic pathways that were identified could be future targets for therapies to improve responses for vaccination, particularly in older adults,” said Albert Shaw, professor of medicine and senior author of the paper.
Even when the influenza vaccine is a good match for currently circulating strains of the virus, most vaccines are less effective for older adults, Shaw said. In fact, roughly 90 percent of deaths from influenza in the country occur in people older than 65, Shaw said.
Shaw said he and his team wanted to identify patterns of gene expression that were found in older and younger adults who showed excellent responses to vaccination and compare those patterns to those who had poor responses to vaccination.
They found specific patterns of gene expression that corresponded to antiviral responses, including those that reflected activities of cells that make protective antibodies against the influenza strain and vaccine, he said. Although antibodies were created about seven days after vaccination for young adults, for older adults, the timing varied, he added.
The study’s findings were not news to representatives from leading vaccine development companies.
“It is well known in our industry that the elderly mount less of an immune response to vaccination,” said Charles Altman, head of medical affairs at BioCSL. “If you look in any product label, you will find that.”
Many manufacturers are trying to improve elderly response, but they face limited options for innovation due to regulations put forth by the World Health Organization, which makes a recommendation each year about which viral strains manufacturers can put in vaccines.
Because manufacturers are not allowed to modify which viral strains they use in their products, they can only vary a few factors, among them dosage and added adjuvants — material added to vaccines to promote immune response — Altman said. Therefore, the study has little practical relevancy for manufacturers like BioCSL.
According to Rachel Felberbaum, director of corporate communications for Protein Sciences, protein-based vaccines allow the same flu block to be given to adults ages 18 and over, and does not have as many side effects as virus-based vaccines.
The active ingredient used in the Protein Sciences vaccine is the HA protein, which has a very well established correlation with antibody levels — the more HA given, the more antibodies, making it a particularly effective vaccine for older people. These antibodies protect against influenza viruses such as H1N1 (otherwise known as swine flu) as well as the recently more common H3N2 strain of Influenza A, said Felberbaum.
The study was conducted on a relatively small cohort, selected on the basis of either very good or very poor vaccine response. Because the study was carried out on a group of relatively healthy group of older adults, the team is interested in exploring how gene expression patterns following vaccination are altered in adults who have chronic medical conditions.
“We’re a ways off from specific therapies, but I think this is the beginning in understanding how age or sex responds to influenza vaccination,” Shaw said.
The research was funded by the National Institute of Allergy and Infectious Diseases at the National Institutes of Health as part of the Human Immunology Project Consortium.