The Centers for Disease Control and Prevention announced the total death count from the 2023-2024 flu season and revealed it to be one of the worst for child deaths in U.S. history. 199 children died—the same as in the 2019-2020 flu season. The highest child death toll from a flu season occurred in the 2009-2010 season, when 288 kids died during the height of the H1N1 swine flu pandemic.

The CDC reported that most of the 199 children who died from the flu during last year’s season were eligible to be vaccinated, but didn’t receive the shot. Annual flu vaccines aren’t foolproof against the virus, but numerous studies show that they’re safe and extremely effective at preventing serious illness. The CDC recommends the annual flu vaccine for anyone six months and older, especially those who are at higher risk for serious illness from the flu, like people who have asthma, diabetes, or obesity.

“It’s hard to watch,” Dr. Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia, told USA Today. “There was a way to prevent this.”

Offit added that many officials are still contending with vaccine hesitancy and misinformation that took hold during the COVID-19 pandemic. That was on top of the way that COVID disrupted many families’ routines — including regular visits to their doctors, where many would have gotten annual shots like flu vaccines.

CDC data showed that out of the 199 children who died, 158 were eligible for a flu shot and had a known vaccination status. Out of those, 131, or 83%, were not vaccinated against the flu.

189 of the children who died had known information on medical conditions. Out of those, 93, or 49%, had at least one pre-existing medical condition that made them high-risk for flu complications.

126 of the children who died were between the ages of 5 and 17. 73 of them were under five years old. Children under five are at greater risk of complications from the flu, like developing bronchitis or pneumonia.

The CDC also reports that flu vaccination rates continue to decline. As of May 11, only 53% of children between six months and 17 years old were vaccinated against the flu, compared to 56% last season. Before the pandemic, 62.4% of kids were vaccinated.