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It’s the end of the influenza season that never began. Typically, by April or May, flu cases start to plummet. But this past year, they never peaked. It’s the result of social distancing, masking and school closings.

But will the flu return with a vengeance or has Covid changed the virus forever?

“This year we have had one admission to the hospital with serious influenza,” NorthShore University HealthSystem’s Dr John Erwin said.

During the flu season that never was, Covid mitigations stopped the seasonal virus from spreading.

“Normally during flu season the hospital is completely packed with the flu,” Erwin said. “We can have thousands of cases in the hospital at any given time depending on the year.”

“In a typical year by this point in time, we’d probably seen maybe 10 kids in the hospital for severe complications and maybe 10 times that being tested for flu and being flu positive,” Lurie Children’s Dr. Tina Tan said.

In a normal season, up to 150 children die from the flu in the U.S. In adults, that number ranges from 12,000 to 61,000 deaths, with up to 45 million cases overall.

“We’ve been imploring people for years to social distance a little bit during flu season, wash their hands, stay home when they are sick,” Erwin said. “And I think the first time in history people are actually staying home when they are feeling sick and I think that has had a lot to do with it.”

Preparations are already underway for the 2021 flu season. The strains in circulation today – even though cases are few in number — get included in next season’s vaccine. The World Health Organization determines the formula, then manufacturers hit the assembly lines.

Dr Gregg Sylvester is with health and vaccine company SEQIRUS.

“In influenza we know there is a thing called antigenic drift, that during the course of an influenza season, the actual virus might drift from what they had predicted,” he said. “That’s what makes it an interesting disease but also more difficult to target our vaccines.” 

MRNA technology helped manufacturers rapidly produce a COVID-19 vaccine. If a future flu season’s dose misses the mark, might it be possible to apply the same technology to a booster designed to address a circulating strain not included in the original selections?

“MRNA technology has been around for a number of years. It was so fortunate it had been and that it worked so well with COVID,” Sylvester said. “We are taking those lessons learned and trying to incorporate them. It’s not an apples-to-apples comparison. There’s one virus they are looking for and four viruses we’re looking for, so we have to be careful. … But future is brighter. It may not be next year. It may be further down the line.” 

So, while the flu may be down for the count, doctors say don’t count it out.

“I don’t see the flu becoming eliminated, but through the course of history we’ve seen viral resp illnesses adapt to change and thwart us, so we have to be mindful of that,” Erwin said.

“It is definitely not sustainable,” Tan said. “But it does show you that social distancing and mask wearing and hand hygiene does work.”

Influenza vaccines have already shipped to the southern hemisphere, where the flu season is about to begin. Experts will be watching closely to see if cases there remain low during 2021.