Atlanta—Especially during severe influenza seasons, the high-dose vaccine is more effective in preventing deaths in older adults, compared with standard-dose vaccines, suggests a study led by CDC researchers.

Background information in the report, published in The Journal of Infectious Diseases, notes that older adults are at high risk for serious complications from flu and account for most of the flu-related deaths and hospitalizations. That is especially the case with H3N2 influenza viruses, which have been associated with higher mortality than infections by H1N1 or influenza B viruses, according to the CDC.

During the 2012-2013 season, when H3N2 viruses were dominant, high-dose flu vaccine was 36% more effective at preventing deaths in the Medicare beneficiaries studied, compared with standard-dose vaccine, the study finds.

The article cites past research that also linked use of the higher dose vaccine with lower rates of office visits and hospitalizations from influenza.

Over the last few years, between 71% and 85% of flu-related deaths occurred among people aged >65 years, according to public health officials. “This is the population that everybody worries about,” explained lead author David K. Shay, MD, MPH, of CDC’s Influenza Division. “Many of the most serious outcomes of flu infections occur in older people.”

In the study, researchers from CDC, the Centers for Medicare & Medicaid Services, and the FDA analyzed data from Medicare beneficiaries who received either the high-dose flu vaccine, which was approved in 2009 in the United States for adults 65 and older, or standard-dose formulations during the 2012-2013 and 2013-2014 flu seasons from community-located pharmacies. More than a million recipients of each vaccine type were studied in each of the two seasons.

Results indicate that, during the 2012-2013 season—when especially dangerous H3N2 influenza viruses were predominant—those who received the high-dose vaccine were 36% less likely to die in the 30 days following hospitalization or an emergency department visit that included a flu diagnosis, compared with the standard-dose vaccine.

The next season, however, the high-dose vaccine was not significantly better at preventing deaths among the Medicare patients studied. Researchers posit that is because H1N1 viruses dominated and because the standard-dose vaccine had better effectiveness than the previous season.

“The high dose vaccine does appear, at least in this particular H3N2 season, to be more effective at preventing deaths that occur within 30 days of an influenza hospitalization,” Shay pointed out. “We didn't see a significant effect on post-influenza deaths during the 2013-2014 H1N1 season.”

« Click here to return to Weekly News Update.