About half the country is experiencing high flu activity, showing early indication this flu season may be severe, according to the U.S. Centers for Disease Control and Prevention.

Young children and people aged 65 years or older are more likely to contract the flu viruses. Although the U.S. experiences epidemics of seasonal flu each year, the CDC reports the virus is showing more elevated activity this year than in previous years. Predictions show flu season may continue to peak.

Nearly 21 children in the U.S. have died from influenza so far, CBS News reports.

CDC recommends people get vaccinated if they have not done so already because it can provide protection and might reduce severe outcomes like hospitalization and death.

Although flu vaccinations are recommended, only one-third of this year's epidemic will be protected.

"In the average year we see effectiveness of the vaccine at 50 to 70 percent, and so it might be a little lower this year," Dr. Joseph Bresee of the CDC told CBS News. "But even if its lower, it still may provide some protection, which is especially important in people at high risk for severe disease."

This year's strain of the influenza virus is not well-matched to the current vaccine, which is why flu shots are less effective in 2015.

"It's concerning because a lot of these patients are coming in and had been vaccinated," Dr. Robert Glatter of Lenox Hill Hospital in New York City said, adding his emergency room sees about 10 patients a day with serious flu symptoms.

The Washington Post reports this is one of the worst flu seasons in recent memory. December alone made one of the worst flu months in the past seven years.

It is possible the flu would get worse since January and February are usually the worst months for flu reports.

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