Since 2010, the U.S. Centers for Disease Control and Prevention has recommended yearly jabs for every healthy American over the age of six months.
The goal is to curb the spread of infection and minimize the risk for potentially dangerous complications such as pneumonia, particularly among the elderly and the very young.
But science on the vaccine’s efficacy is scant among those two vulnerable groups. And although healthy adults do get some protection, it may not be as robust as they expect.
One oft-cited claim, based on several large meta-analyses
published more than a decade ago, is that seasonal flu shots cut the risk of winter death among older people by half. But the research behind that claim has been largely debunked.
A 2005 study
published in the Archives of Internal Medicine
noted that influenza
only causes about 5 percent of all excess winter deaths among the elderly—which works out to one death from flu per 1,000 older people each season—so it’s impossible for the shot to prevent half of all their winter deaths. The following year, a study
reported that as vaccine coverage increased among the elderly in Italy in the late 1980s, there was no corresponding drop in excess deaths.