Flu Vaccine in Adults Provides Extra Protection for Elderly

Adults who get immunized against influenza are protecting not only themselves, but also their elderly peers.

The elderly are most at risk for flu-related morbidity and mortality because of their weakening immune systems.

Although the flu vaccine is less effective in this population, new research shows that immunization among younger adults is inversely associated with flu-related illnesses in the elderly. This association was especially strong among elderly patients who also received the flu vaccine, as the reduction in risk for flu-related illness was twice as large for seniors who were vaccinated against the flu.

The study examined 520,229 adults ages 18 to 64 using county influenza vaccination coverage data from the Behavioral Risk Factors Surveillance System Survey, and then compared the findings with the incidence of flu-related illness in about 3.3 million Medicare recipients ages 65 and older between 2002 and 2010.

In counties where at least 31% of the younger population was vaccinated, the elderly had 21% lower odds of developing a flu-related illness. On the other hand, in counties where 15% or less of the younger adult population vaccinated, the elderly had a 9% lower chance of developing a flu-related illness.

The link between greater populations of vaccinated young adults and lower incidence of flu-related illness in elderly patients was stronger in peak months of the flu season, more severe flu seasons, and flu seasons with greater antigenic match to the flu vaccine.

“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 study author Glen B. Taksler, PhD, of the Cleveland Clinic in a press release. “In round numbers, we estimated that about 1 in 20 cases of influenza-related illness in the elderly could have been prevented if more non-elderly adults had received the flu vaccine.”

The researchers did not find evidence of a similar link between children’s flu vaccine coverage and flu-related illness in the elderly.

While the study results do not show a causal relationship, Dr. Taksler stated that they could help health care professionals educate patients about the benefits of immunization against the flu.

More than 40 million doses of this year’s flu vaccine have already been distributed, and they should be a better match to the circulating viruses, according to the US Centers for Disease Control and Prevention (CDC).

The CDC advises all patients ages 6 months and older to receive an annual flu vaccine.

This study was published in Clinical Infectious Diseases.