Brace yourselves: the upcoming 2021-2022 flu season could be a nasty one — especially for young kids — as a result of dwindling population-level immunity from the relatively puny 2020-2021 flu season during last winter’s surge of COVID-19.
Two new preliminary analyses have used mathematical modeling to predict the 2021-22 flu season and found the US is likely to have around 20 percent more flu cases than normal. Under a worst-case scenario, there could be double the number of flu cases than a typical year.
The two papers — which have not yet been peer-viewed — can be found on the preprint server medRxiv here and here. Their models suggest that this winter will likely bring around 600,000 hospitalizations from influenza in the US, over 100,000 more than would happen in a typical season. Paired with the ongoing COVID-19 pandemic, this could mean real trouble for health infrastructure.
The severity of the situation will largely depend on how many people get the flu shot. If vaccine uptake is extremely low, for instance, they predict the US could see an extra 400,000 hospitalizations. To avoid overburdening hospitals, the research indicates that up to 75 percent of the US should be vaccinated against flu, rather than the typical 50 percent.
“The ‘twindemic’— a coinciding flu and COVID-19 epidemic — overwhelming our hospitals was thankfully avoided last year. But that does not mean it is no longer possible,” Professor Mark Roberts, director of the Public Health Dynamics Laboratory at the University of Pittsburgh and senior author on both studies, said in a statement. “If anything, our models show that we should be more concerned this year about the possibility of a surge in COVID-19 hitting at the same time as a massive flu outbreak in areas of the country with low vaccination rates against both diseases.”
The 2020-2021 flu season was practically non-existent, namely because communicable infections, such as flu, were inadvertently quashed with social distancing and other COVID-19 control measures. In fact, these measures were so effective at halting communicable infections that a few flu strains may have become extinct in human populations.
However, just as many scientists feared, the flu is set to come back with vengeance this year. Flu shots are created each year base on the predicted most virulent strains doing the rounds, which is why you should get a new one each year — they target different strains. Since very few people caught the flu over the winter of 2020-2021, immune systems were less likely to be confronted with the virus and population-level immunity has significantly waned. Young children are thought to be especially at risk since they are unlikely to have had any previous exposure to flu bugs.
Predicting the flu season is always a notoriously tricky process, even in the best of times, so these estimations should not be considered cold hard facts. Nevertheless, all signs currently suggest the 2021-2022 flu season is likely to be rough. According to the Centers for Disease Control and Prevention (CDC), "Reduced population immunity due to lack of flu virus activity since March 2020 could result in an early and possibly severe flu season."
To dodge overfilling hospitals, health experts are strongly recommending as many people as possible to get the influenza vaccine (and, of course, the COVID-19 vaccine, if they haven't already).
“This is not to suggest that we should stop COVID-19 mitigation efforts to avoid a severe future flu season,” added Professor Roberts. “Instead, it shows that more of us—particularly young children—will be susceptible to the flu and that vaccination is absolutely essential to avoiding bad outcomes."