A Food and Drug Administration advisory committee voted Thursday to recommend including a viral strain of the flu, subclade k, in vaccines beginning this fall.
It’s something that the World Health Organization also suggested, as the variant is likely one reason flu vaccines were less effective this year.
The Centers for Disease Control and Prevention, in its Morbidity and Mortality Weekly Report (MMWR), reported that influenza vaccine effectiveness was 38% to 41% for preventing outpatient visits for children and adolescents and 41% for preventing hospitalization.
For adults, that number is at 22% to 34% against influenza-associated outpatient visits and 30% against influenza-associated hospitalization.
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Although those numbers were lower than during recent flu seasons, “these findings demonstrate that influenza vaccination still provides protection against influenza,” the CDC noted, adding that it still recommends people get inoculated. During last year’s flu season, vaccinations prevented an estimated 5 million medical visits, 180,000 hospitalizations and 12,000 deaths, the CDC said.
The CDC estimates the flu caused at least 26 million illnesses, 340,000 hospitalizations and 21,000 deaths between last Oct. 1 and Feb. 28.
Dr. Lisa Grohskopf, a medical officer in the CDC’s Influenza Division, said at the committee’s meeting that subclade K is the dominant flu variant in the Northern Hemisphere this year.
As the University of Minnesota’s Center for Infectious Disease Research and Policy notes, though, viruses mutate frequently, meaning that there’s no guarantee that variants selected at this recent meeting will be the same ones that spread during the next flu season. Vaccines take about six months to develop, which is why scientists decide on their formulation in February or March.
“We’ve had a very efficient meeting in a very complicated year where we were reminded about how difficult strain selection is,” Arnold Monto, a University of Michigan epidemiologist and the Vaccines and Related Biological Products Advisory Committee acting chair, said, according to Politico. “It’s a little bit of science, a little bit of luck.”
What is subclade K?
As Straight Arrow News previously reported, subclade K is a newly emerged subgroup of a common flu strain that has plagued humans for decades. It is within the H3N2 family, according to Yale Medicine.
It was behind the earlier-than-usual surge of flu cases in the U.S., Japan and the United Kingdom, as well as other places in Europe.
Health officials in the U.K., citing preliminary flu data, said that subclade may spread easier than other versions of the illness, leading to more hospitalizations and test positivity.
“By some metrics, this is the worst we have had in years and possibly, decades in terms of inpatient flu numbers and test positivity rates at the hospital,” Dr. Scott Roberts, a Yale Medicine infectious diseases specialist, said in a statement.
Still, Roberts says he hasn’t seen data indicating that this subclade is more severe than others.
“The reason people are saying ‘super flu’ is because it’s a bad flu wave and many people are getting infected and hospital admissions are high,” he says. “That’s all reflective of the fact that it’s more mutated and there’s increased transmissibility, not that it’s more severe.”
