IOWA CITY, Iowa (CNN) – The day before Christmas, a healthy four-year-old little girl had to be airlifted to the children’s hospital at the University of Iowa as her parents watched in horror.

Jade had the flu, a strain called influenza B.

It’s spreading quickly across the country, which is highly unusual for this time of year, and experts say the most vulnerable to it are children.

In the pediatric intensive care unit, the Jade was unresponsive, a ventilator breathing for her.

Dr. Aditya Badheka said, “Influenza B is activating her own immune system, to start attacking her own organs, specifically the brain and causing brain swelling.”

For days, Jade’s mom and dad didn’t know what the future would bring.

Her doctors feared she might not make it.

Then finally, after nearly two weeks, Jade woke up.

But doctors noticed something, Jade can’t see.

The flu caused inflammation in her brain, and she may be blind forever.

Her parents know jade still has a long way to go in her recovery, and they’re stunned by what the flu can do to a healthy child.

Jade went home from the hospital on January 9th.

Her mom says both Jade and her sister received a flu shot last March.

She thought that shot was good for an entire year.

She didn’t realize she needed to get the girls vaccinated again for the new 2019-2020 flu season.

Since the flu virus changes year to year, the vaccine also changes.

Flu vaccines become available at the end of the summer, and the CDC recommends getting one by the end of October to protect against flu in the upcoming winter.

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