Baby boomers are the second-most impacted group for flu hospitalizations this season, in a surprising shift from previous years when the most vulnerable groups are the elderly and young children.
Adults aged 50 to 64 have the second highest rate of hospitalizations, 44.2 per 100,000, for influenza or pneumonia, according to the latest flu surveillance report compiled by the Centers for Disease Control and Prevention.
“Baby boomers have higher rates [of hospitalization] than their grand children right now,” said Dr. Dan Jernigan, the director of the influenza division of the CDC, in a briefing with reporters.
Their rates of hospitalization are higher than the two previous seasons where H3N2 was the predominant viral strain, 2012-13 and 2014-15.
While experts categorize H3N2 as a particularly bad actor, able to mutate and adapt faster than vaccines can be developed against it, Dr. Jernigan said this age group is equally testing positive for the H1N1 strain, about 20 percent of cases.
“I think, H1N1 is providing an additional contribution of cases in that 50- to 64-year-old range. In addition, we’re seeing flu higher in that 18-49 year range as well,” he said.
The rising rates of H1N1, particularly among Baby Boomers, have scientists further exploring a theory called “imprinting,” the idea that whatever influenza viral strain people are exposed to as children will set them up for protection later in life.
During the 2009 pandemic, there was a record low number of infections and hospitalizations among those aged 65 and older. Scientists believe this group was exposed to the H1N1 strain early in their lives.
“So between 1918 to 1947 when that H1N1 was circulating, people that were exposed to that one seemed to respond better when this 2009 H1N1 showed back up,” Dr. Jernigan said.
The same can be said on the other side, he continued, and that people born after 1947 were exposed to the H2N2 and H3N2 circulating strains, which make them more vulnerable to H1N1.
“I think it shows just the complicated nature of influenza,” he said, “that it really depends on a mixture of things — the environment, the virus itself and how it changes, but also the host, the changes that occur as people get exposed to different influenza virus’s over time.”
As for the rest of the season, Dr. Jernigan said they’ve observed a “sharp increase” in the death rate, with 9.1 percent of all deaths contributed to either pneumonia or flu.
Yet this number is lower than death rate during the 2012-13 and 2014-15 seasons at the same peak time — which were at 11 and 11.8 percent respectively.
At the same time, rates of infection and hospitalization are trending similar to 2014-15, Dr. Jernigan said, deemed a “higher level of severity”. In that year there were an estimated 34 million infections, 710,000 hospitalizations and 56,000 deaths.
“We haven’t reached those peaks yet but it’s still early in the season,” he said. “So we maybe getting to that level or maybe even surpass those numbers as the season progresses.”
Health experts recommend for people to still get vaccinated if they haven’t already. Practicing good hygiene — washing hands, covering coughs and sneezes and limiting physical contact — all help stem the spread of flu.
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