A year full of social distancing, mask wearing, hand washing and staying at home to prevent coronavirus spread rendered the 2020-2021 influenza season practically non-existent.
Public health and clinical laboratories reported 2,038 flu cases during the season from Sept. 27, 2020 to April 24, 2021, according to the Centers for Disease Control and Prevention. Meanwhile, the agency estimates about 38 million people were sick with the flu during the 2019-2020 season.
“It’s been an amazing year,” said Dr. John Swartzberg, a professor emeritus of infectious diseases at the University of California-Berkeley in the school of public health. “In all my years of being a flu watcher … I’ve never seen anything like this.”
While low flu incidence is unarguably a good thing, it raises questions about the upcoming flu season and what the flu vaccine will look like in the fall.
Twice a year – once in February and once in September – the World Health Organization meets with health experts to review last season’s flu data. Together, they predict the four most common strains in the upcoming flu season and recommend what vaccine manufacturers should include in the next flu vaccine.
But this year, researchers are working with very little data, as international efforts to slow the coronavirus pandemic has drastically reduced flu cases across the globe.
“Normally and unfortunately, we have a wealth of data to base the next year’s flu vaccines on,” Swartzberg said. “But we don’t have a lot of that this year.”
Based on the available data, the WHO recommended a flu vaccine that looks similar to last season’s, he said, “which makes sense because a very small percentage (of people) on this planet developed immunity to last year’s strains.”
In a quadrivalent vaccine – which contains four flu strains – the WHO recommended vaccine manufacturers keep two B strains and change out two A strains in the new vaccine, said Dr. Gregg Sylvester, chief medical officer at Seqirus, a cell-based influenza vaccine manufacturer based in North Carolina.
“Will they get it right? That will be hard to predict,” he said.
As manufacturers ramp up production of flu vaccine, many Americans wonder what the upcoming season will bring. Health experts predict the virus will stick to its regular seasonality, appearing in early October and ending by April, lasting on average about 13 weeks.
The lack of flu cases this season shouldn’t impact the upcoming flu season, Swartzberg said. The fact that many people didn’t get sick during an unusual flu season doesn’t mean their immune systems have weakened and are unprepared for a normal season.
“It’s not like what doesn’t kill you makes you stronger,” he said. “We don’t need to be exposed to influenza on a regular basis and get sick to have stronger immune systems.”
It’s difficult to make any other predictions about the 2021-2022 flu season right now, especially as the country continues to struggle with coronavirus cases, which hover around 50,000 new cases per day, according to the CDC.
We don’t know if reopening will trigger a bad flu season, Sylvester said, “but we ought to be prepared for it.”
Swartzberg hopes the pandemic has taught Americans about the importance of public health and how safety measures can be used for other viruses, not just SARS-CoV-2.
“If we learned enough from this COVID pandemic, maybe everybody will always wear masks if they have a runny nose … maybe businesses will allow them to stay home and not force them to come to work,” he said. “It could really make us a lot healthier.”
Follow Adrianna Rodriguez on Twitter: @AdriannaUSAT.
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