To find out if flu shots really save lives in nursing homes, researchers used the year-to-year variability in the flu vaccine’s effectiveness to their advantage. Their results show the better matched the vaccine was for the influenza strain, the fewer nursing home residents died or were hospitalized between 2000 and 2009.
“Ours is the first study to, we think, come up with an unbiased approach.”
If vaccines don’t help the elderly, as some critics suggest, then nursing home residents shouldn’t fare any better when the vaccine is a good match than when it’s a bad match.
“What we’ve used is the randomness of the match,” says Vincent Mor, corresponding author of the study and professor in the Brown University School of Public Health. “Ours is the first study to, we think, come up with an unbiased approach.”
‘That’s saving lives’
The match rate varied particularly widely in the flu strain A/H3N2, which is typically the strain that leads to most flu hospitalizations and deaths. Over the 10-year study period, the match rate ranged from 11.2 percent in 2003-2004 and 22 percent the next year, to 100 percent in the first two study years and in the last one. Match rates for strain A/H1N1 were usually very high and for strain B were usually low.
By comparing weekly deaths and flu-related hospitalizations in each year’s flu season, the researchers were able to calculate that for every percentage point increase in the A/H3N2 match rate, weekly deaths declined by about 0.0016 and hospitalizations declined by about 0.002 per 1,000 nursing home residents.
Those numbers may seem small, but put another way, among about 1 million elderly people living in nursing homes each year, a 50-percentage point increase in the match rate for a flu season would save the lives of 2,560 people and prevent 3,200 hospitalizations.
“That’s saving lives,” Mor says. “That’s really a profound effect.”
The results are likely applicable to all elderly people, the vast majority of whom do not live in nursing homes, he says. Vaccination rates among the elderly in the community, however, tend to be much lower than in nursing homes.
“This study evidences protection for an elderly population for whom vaccine efficacy has been questioned,” says coauthor Stefan Gravenstein, adjunct professor of medicine and health services, policy and practice. “Annual vaccination is the only way to maximize the benefit of vaccine, no matter what the age.”
Aurora Pop-Vicas, clinical assistant professor of medicine, is the study’s lead author. The Agency for Health Care Research and Quality funded the work, which appears in the Journal of the American Geriatrics Society.
Source: Brown University