Older people, believed to be at greater risk for developing severe flu symptoms this season, should seek a high-dose vaccine instead of the standard dose even if they are frail and in long-term care, researchers say.
Federal officials approved the high-dose vaccine for people ages 65 and up about five years ago. It was first tested on independent, healthy older adults with an average age of 73 years – and proved successful at triggering stronger immune responses.
Now, new data show that the high-dose vaccine outperformed the standard dose in residents of long-term care facilities with an average age between 86 and 87, according to University of Pittsburgh researchers. The findings are considered promising, as the predominant virus has already mutated, making for a challenging flu season for ailing older people.
Public health officials did confirm, however, that it’s hard to predict the ultimate severity of the season. In the Sacramento region, flu activity generally remains low but is picking up, said Dr. Randy Bergen of Kaiser Permanente’s Northern California operation.
In the Pennsylvania facilities studied, all 205 residents tested were dependent on caregivers to help them with their daily activities. Many had cognitive impairments and walked at the slow speed of 0.7 meters per second, a gait that is considered a measure of frailty. In these respects, researchers said, they were typical of long-term care patients anywhere in the United States.
“Even in the frail, long-term care population, the high-dose flu vaccine looks like it produces a greater antibody response than the standard dose vaccine,” the university’s Dr. David Nace said in a statement.
Nace noted that long-term care patients can be especially vulnerable to flu viruses because they live in closed spaces, with caregivers and family members coming and going, possibly exposing them to viruses. Recent results showed that the institutionalized patients developed higher antibodies about 30 days after being inoculated, with no signs of serious adverse side effects.
Public health officials early on singled out older people as being particularly susceptible to the currently circulating Influenza A virus, H3N2, and its mutated cousin. In past years, the notorious H3N2 virus led to death rates more than double that of other flu seasons, experts say.
The Centers for Disease Control and Prevention also is emphasizing that very young children, too, may suffer disproportionately if exposed to H3N2. Already, four infants have died of the flu in the U.S. this season.
Complicating the infectious-disease landscape is the discovery that strains of H3N2 have developed mutations resisting the protective antibodies that develop after immunization. CDC experts say that about half of the H3N2 viruses in circulation were infiltrated by slightly different strains. The resultant changes to the virus’ genetic code makes the rogue H3N2 mutated strain unrecognizable to antibodies.
If this season’s antibodies were watchmen on duty to quash the H3N2 flu virus in vaccinated people, they’d be blind to the threat of the mutated H3N2 virus and let it slide on by, said Dr. Ivan Oransky, a leading physician and global editorial director of MedPage Today.
“The immune system is being finely turned by that vaccine,” Oransky said. “If the shade or shape of the virus is a different shade or shape than it was trained to block, the antibodies won’t work.”
Oransky said while mutations are not necessarily rare, it’s unfortunate when they occur after vaccines have already been developed for a particular season.
“Viruses do mutate, and sometimes the mutations turn into viruses that can’t be reproduced” in time to reformulate new vaccines. It’s the way of the natural world, Oransky said: “It’s Darwin; it’s evolution.”
The mutations, called drift variants by researchers, are showing up in the majority of flu specimens tested so far this year. CDC officials say this makes for a rough severe flu season. They recommend that everyone 6 months old and up be vaccinated because the original H3N2 is still out there, and developing some antibodies is better than none at all.
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