A high-dose flu vaccine may offer more protection to older adults during flu seasons in which Influenza A(N2N3) is circulating.
Not all flu vaccines are created equal. In 2009, the US Food and Drug Administration (FDA) licensed a vaccine containing more antigen than the standard flu vaccine. Designed to be given to adults 65 years and older, given this population’s increased risk of dying from flu, the vaccine was approved and rolled out for distribution. But did this high-dose flu vaccine actually do a better job of preventing influenza deaths among older adults?
A team of researchers at the Centers for Disease Control and Prevention (CDC), the Centers for Medicare and Medicaid Services, and the FDA examined records from the 2012-2013 and 2013-2014 flu seasons in the United States. Included in the study were Medicare recipients who were at least 65 years of age and who received either a high-dose flu vaccine or a standard flu vaccine in local pharmacies that were offering both types. The study was broad­— the researchers looked at data on 1,039,645 senior citizens who received the high-dose shot and 1,683,264 who received the standard shot in 2012-2013. For the 2013-2014 flu season, data on 1,508,176 high-dose vaccine recipients and 1,877,327 standard-vaccine recipients were examined. Study participants in both groups had similar prior health conditions and economic status.
During both flu seasons, 83 post-influenza deaths occurred among the group receiving the high-dose vaccine and 162 deaths occurred in the standard-dose group (post-influenza death was defined as a death occurring within 30 days of a Medicare claim being filed for a hospitalization or ER visit due to influenza). There was a 36% reduction in deaths among the high-dose vaccine recipients during 2012-2013, along with a 20% cut in flu-related doctor visits and hospital flu diagnoses. However, no significant reduction in deaths occurred among the high-dose vaccine recipients in 2013-2014, only a significant reduction in the rate of hospitalizations due to influenza. According to the researchers, this lack of a significant reduction in flu deaths was due, in part, to the circulating flu strain during that period.
“Influenza A(H3N2) viruses, which are usually associated with higher mortality in older adults, were predominant during [the 2012-2013 flu season],” said David K. Shay, MD, MPH, a medical officer at the CDC and an author of the study. “During the following season (2013-2014), Influenza A(H1N1) viruses dominated. Data from other studies demonstrated that the standard-dose vaccine had better effectiveness than [the one used during] the previous season. We did not find evidence during the 2013-2014 H1N1-dominated season that the high-dose vaccine was significantly better at preventing deaths among the Medicare patients studied.”
It’s well known that those age 65 and older are at highest risk of serious complications—and even fatalities—due to flu. According to the authors, when Influenza A(H3N2) is the predominant virus, as it was during 2012-2013, older adults present with worse outcomes than when other strains of flu are in circulation. Therefore, they suggest that during seasons in which Influenza A(H3N2) is going around, older adults may benefit from receiving high-dose vaccines instead of standard-dose vaccines.
The CDC currently does not recommend a particular flu vaccine for those age 65 and older, only that this population get a vaccine; nevertheless, it may be prudent to seek out the higher-dose vaccine for the most protection.
Laurie Saloman, MS, is a health writer with more than 20 years of experience working for both consumer and physician-focused publications. She is a graduate of Brandeis University and the Medill School of Journalism at Northwestern University. She lives in New Jersey with her family.