Americans could face a severe influenza season in the new year, as a new flu variant spreads and current vaccines seemingly offer limited protection.
Frederick Hayden, a professor emeritus at UVA’s School of Medicine, said available flu vaccines appear to be a poor match for the H3N2 subclade K virus that has already begun circulating in the U.S.
“Now, the particular virus that we're concerned about currently is accounting for about three quarters of all the circulating strains that have been characterized in the United States,” Hayden said.
Recent data suggest flu activity is picking up. A December update from the Centers for Disease Control and Prevention shows transmission is accelerating nationwide, with an estimation of at least 49,000 flu-related hospitalizations and about 1,900 deaths so far this season.
Hayden said the virus is likely to gain momentum during holiday travel and gatherings, then spread further once schools reopen after winter break.
While vaccine effectiveness may be lower than hoped, Hayden said people should still get them.
“People will have a much lower risk of having severe illness,” Hayden said. “They may not prevent them from getting the influenza entirely, but it will diminish the risk of having a severe outcome. The more vaccines that we can get across the population, then we'll have this secondary effect of reducing transmission of the virus.”
Haden and British virologist Marina Zambon examined flu trends in other countries for a study published in the Journal of the American Medical Association this month.
The study looked at nations including the United Kingdom, where the U.K.’s National Health Service has warned that flu hospitalizations in that country are the highest they’ve ever been this time of year.
Early data from the U.K. shows this season’s flu vaccines, though offered less protection against the subclade K than hoped, still significantly reduce severe outcomes.
According to preliminary estimates, injected flu vaccines for adults lowered the risk of flu-related emergency department visits and hospitalizations by more than 30%.
Among children, who primarily receive the intranasal flu vaccine in the U.K., effectiveness was substantially higher, reducing those outcomes by more than 70%.
Besides getting vaccinated, taking basic precautions as flu activity rises are the best ways to avoid getting sick. That includes avoiding close contact with sick individuals, washing hands regularly and wearing masks in crowded indoor settings when appropriate will reduce exposures, Hayden said.
Antiviral medications can help prevent illness after exposure and reduce complications if taken early, he said.
