Low immunity could lead to a high risk of flu, health officials warn

Fewer cases of the flu last season could lead to more outbreaks this season, public health officials warn.

That’s because when the flu spreads it also increases the prevalence of immunity within the population.

During last season's peak, which in Florida is typically in January and February, many people were wearing masks and social distancing to avoid spreading COVID-19.

That led to far fewer cases of the flu.

“Masking and social distancing interrupted the spread of influenza in the community and the decrease in international travel stopped influenza clients from entering the United States like in New York, California, Florida, Texas, etc.,” said Dr. John Sinnott, Chairman of Internal Medicine at the University of South Florida, Morsani College of Medicine and an epidemiologist at Tampa General Hospital. “It really limited the importation of influenza.”

But that also meant the immune systems of the general population weren’t challenged and didn’t build up the immunity to fight new strains of the flu.

“If you were to look historically, every time there's a mild season, it's followed by a severe season,” Sinnott said. "The basis for that is that there is no leftover immunity from the year before. So you will see more people infected and more severe disease.”

Influenza, or the flu, is a systemic illness and prior to COVID-19, 35,000 people a year died from the respiratory infection, Sinnott said.

Data from Florida Department of Health and Centers for Disease Control and Prevention show that only one influenza-associated outbreak has been reported in the state since the end of last season in May.

However, Florida runs a high risk of an outbreak because it has reopened businesses and schools and started holding major events again, Sinnott said.

Sinnott and other health experts are warning that the spread of COVID-19 and influenza at the same time could lead to a “twindemic” that could overwhelm the state’s hospital capacity.

For those susceptible to influenza, the situation could be dire, Sinnott said.

“This is where you have two respiratory viruses with similar symptoms circulating at the same time,” he said. “We have had at Tampa General a couple patients last year with both influenza and COVID and they did very poorly. Some had extended hospital stays.”

To prevent a larger outbreak, Sinnott advised that people get vaccinated for both COVID and the flu.

He recommended getting a COVID booster and the vaccine together as our immune systems are “doubly challenged,” and will get a “synergistic response.”

“Also, you're going to feel bad the next day so might as well just feel bad one day, rather than separate them by a month and feel bad two days,” Sinnott said.

The flu vaccines this year cover all four strains of influenza. People 65 and older will get a stronger dose so they develop a better immune response, Sinnott said.

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