Low vaccination rates may also be contributing to this year’s sick season. As of late January, U.S. vaccine uptake was well below the CDC’s target of 70% coverage, with only about 44% of U.S. adults and children vaccinated. That’s on par with recent seasons for adults, but lower than normal for kids.

The United States is experiencing its most severe flu season in more than a decade, with the U.S. Centers for Disease Control and Prevention (CDC) estimating that there have been at least 24 million influenza cases so far this season.