Here are the flu strains health officials predict could hit hard next season

By Jackie Flynn Mogensen edited by Claire Cameron

This winter’s flu season isn’t over yet, but global health authorities are already preparing for the next one. Last week the World Health Organization (WHO) announced which strains it recommends that vaccine makers produce shots for in order to fend off the virus in the coming year.

The WHO recommended making shots tailored to combating the influenza A subtype H1N1, which is also known as swine flu, H3N2, another subtype of the influenza A virus, and the B/Victoria lineage, which is a type of influenza B virus. Officials also called on researchers to prepare “candidate vaccine viruses” for a form of bird flu, H9N2, in case of a future pandemic.

The WHO’s vaccine recommendation is similar to last year’s. But this flu season, a period that typically begins in October and lasts through the following spring, has been particularly harsh. So far, in the U.S. alone, the virus has caused at least 25 million illnesses and 20,000 deaths, including the deaths of 79 children, according to the U.S. Centers for Disease Control and Prevention. Part of why this season has been so severe has been the emergence of a new variant of the virus known as “subclade K,” which seems to be able to dodge some of the current flu vaccine’s protective effect—although the shot may still offer some defenses, experts say.

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The WHO also warned that flu viruses that usually only infect animals, including bird flu, have sickened at least 25 people across six countries since last September. “The majority of these cases had been exposed to infected animals or to environments contaminated with influenza viruses,” the organization said. And while the WHO isn’t aware of any human-to-human transmission of such zoonotic influenza, it doesn’t hurt to be prepared with vaccines, experts say.

The WHO’s recommendations have come amid speculation over the future of next-generation flu vaccines. In February the U.S. Food and Drug Administration agreed to review an mRNA flu jab made by the vaccine maker Moderna, which had successfully used the technology in its mRNA COVID vaccines, after the agency initially refused to do so.

An mRNA flu vaccine, which would work similarly to the COVID vaccines, could be manufactured faster than traditional shots, experts say—something that could come in handy if and when new variants like subclade K emerge long after a given year’s flu shot has been produced.

U.S. officials are also backing efforts to make a universal flu vaccine, which, if successful, could offer broad protection against many different strains of the virus.

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