The high-dose flu vaccine appeared to be more effective at preventing post-influenza deaths among older adults than the standard-dose vaccine, at least during a more severe flu season, according to a large study of Medicare beneficiaries.
The findings build on earlier research suggesting that the high-dose vaccine may be better at preventing influenza virus infections and other flu-related outcomes in seniors, including office visits and hospitalisations, compared to the standard-dose vaccine.
Older adults are at high risk for serious complications from flu because of their age. In recent years, between 71% and 85% of flu-related deaths have occurred among people 65 years of age and older, according to estimates from the Centres for Disease Control and Prevention (CDC). The high-dose flu vaccine was approved in 2009 in the US for adults 65 and older. "This is the population that everybody worries about," said study author Dr David K Shay, 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 Centres for Medicare & Medicaid Services, and the US Food and Drug Administration drew on data from Medicare beneficiaries aged 65 or older who received either the high-dose or standard-dose flu vaccine 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.
During the 2012-2013 season, people who got a high-dose vaccine were 36% less likely to die in the 30 days following hospitalisation or an emergency department visit that included a flu diagnosis compared to the standard-dose vaccine, the researchers found.
H3N2 influenza viruses, which are usually associated with higher mortality in older adults, were predominant during that season. During the following season (2013-2014), when H1N1 viruses dominated and the standard-dose vaccine had better effectiveness than the previous season, the high-dose vaccine was not significantly better at preventing deaths among the Medicare patients studied.
"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 hospitalisation," Shay said. "We didn't see a significant effect on post-influenza deaths during the 2013-2014 H1N1 season."
In a related editorial commentary, Dr Arnold S Monto, of the University of Michigan School of Public Health, who was not involved in the study, noted that the findings fit well with previous data showing the high-dose flu vaccine is more effective against uncomplicated flu illness and likely hospitalisations. "This indicates that improvement in our 70-year-old influenza vaccines is possible, and to get there more quickly we should not ignore older technologies while working on more dramatic advances," Monto wrote.
Abstract
Background: Recipients of high-dose vs standard-dose influenza vaccines have fewer influenza illnesses. We evaluated the comparative effectiveness of high-dose vaccine in preventing postinfluenza deaths during 2012–2013 and 2013–2014, when influenza viruses and vaccines were similar.
Methods: We identified Medicare beneficiaries aged ≥65 years who received high-dose or standard-dose vaccines in community-located pharmacies offering both vaccines. The primary outcome was death in the 30 days following an inpatient or emergency department encounter listing an influenza International of Classification of Diseases, Ninth Revision, Clinical Modification code. Effectiveness was estimated by using multivariate Poisson regression models; effectiveness was allowed to vary by season.
Results: We studied 1039645 recipients of high-dose and 1683264 recipients of standard-dose vaccines during 2012–2013, and 1508176 high-dose and 1877327 standard-dose recipients during 2013–2014. Vaccinees were well-balanced for medical conditions and indicators of frail health. Rates of postinfluenza death were 0.028 and 0.038/10000 person-weeks in high-dose and standard-dose recipients, respectively. Comparative effectiveness was 24.0% (95% confidence interval [CI], .6%–42%); there was evidence of variation by season (P = .12). In 2012–2013, high-dose was 36.4% (95% CI, 9.0%–56%) more effective in reducing mortality; in 2013–2014, it was 2.5% (95% CI, –47% to 35%).
Conclusions: High-dose vaccine was significantly more effective in preventing postinfluenza deaths in 2012–2013, when A(H3N2) circulation was common, but not in 2013–2014.
Authors
David K Shay, Yoganand Chillarige, Jeffrey Kelman, Richard A Forshee, Ivo M Foppa, Michael Wernecke, Yun Lu, Jill M Ferdinands, Arjun Iyengar, Alicia M Fry, Chris Worrall, Hector S Izurieta
[link url="https://www.sciencedaily.com/releases/2017/03/170302090843.htm"]Infectious Diseases of America Society material[/link]
[link url="https://academic.oup.com/jid/article/3058746/Comparative"]The Journal of Infectious Diseases abstract[/link]