Adult Flu Vaccination Protects the Elderly

Published in Clinical Infectious Diseases, the study suggested that healthy adults who receive the flu vaccine may not only protect themselves but also older adults in their community who are at higher risk for serious complications from influenza.

For the study, Glen B. Taksler, PhD, an associate staff member in the Medicine Institute at the Cleveland Clinic, and colleagues examined the association between county-wide influenza vaccination coverage among 520,229 adults aged 18 to 64 and illness related to influenza in 3,317,709 elderly Medicare beneficiaries aged 65 and older, between 2002 and 2010.

The study team found the older patients were up to 21% less likely to be diagnosed with flu-related illness when living in areas where at least 31% of younger adults had received the flu vaccine.

When compared with elderly residents of counties where 15% or fewer younger adults have been vaccinated against the flu, the adjusted odds ratios for a principal diagnosis of influence among elderly residents were 0.91 for counties with vaccination rates of 16% to 20% for younger adults, 0.87 for counties with 21% to 25% vaccinated, 0.80 for counties with 26% to 30% vaccinated, and 0.79 for counties with 31% or more vaccinated.

“Our findings suggest that flu vaccination should be encouraged among low risk adults not just for their own benefit, but also for the benefit of higher risk adults in their community, such as the elderly,” said Taksler. “In round numbers, we estimated that about one in 20 cases of influenza-related illness in the elderly could have been prevented if more non-elderly adults had received the flu vaccine.”

When older adults were also vaccinated against the flu themselves, reductions in risk for flu-related illness were more than twice as high for the elderly, when compared with older adults who were not immunized. This finding, according to the study investigators, suggests that community-wide vaccination may increase the protection provided by individual vaccination. However, no associations were found between vaccine coverage among children and flu-related illness in the elderly, suggesting that older patients may benefits most for vaccination coverage of younger adults in their community, with whom they are probably more likely to have direct contact.

Taksler and colleagues pointed out that their findings suggest, but no prove, a causal relationship between higher influenza vaccination rates among younger adults and decreased flu-related illnesses in the elderly. But they believe the study may help inform vaccination policies and patient—provider discussions about the benefits of flu vaccination. Taksler added that the findings, if confirmed in future studies, could have particular relevance in large metropolitan areas, where younger adults “are often in contact with older adults, such as on crowded buses or subway trains.”