(WASHINGTON) — President Joe Biden and members of his COVID task force are using personal stories to persuade young people get vaccinated following up on the Food and Drug Administration authorizing the Pfizer vaccine for children ages 12 to 15 earlier this month.

At Tuesday’s White House briefing, senior coronavirus adviser Andy Slavitt revealed that one of his sons, Zach, who is 19, has serious lingering effects from COVID-19 — six months after he first tested positive.

“Last fall, one of my sons contracted COVID-19. Unfortunately, he is one of the many Americans battling long-term symptoms,” Slavitt said.

“He’s young and fit and in the prime of his life. But six months later, he still suffers from tachycardia, shortness of breath, and ongoing and frequent flu-like symptoms. His hands are cold to the touch. Neither he nor his parents — my wife and I — are sure how long this will last,” Slavitt continued, speaking of the younger of his two sons. “Many young people are in this situation, and many, many have it worse.”

Slavitt said he knows it may be easy for young people to think COVID-19 doesn’t affect them because they may feel healthy and be asymptomatic but emphasized that experts still don’t know enough about the long-term effects of the disease.

“A vaccine may feel unnecessary. You feel healthy, you know people who have had COVID and are doing all right. But we are still learning about the long-term effects of COVID,” Slavitt added, in a personal plea to increase young adult vaccinations across the country.

According to the Centers for Disease Control and Prevention, more than 3 million kids under 17 have contracted COVID-19, Slavitt said, “and even though it’s rare for kids to get severely ill from COVID-19, it can happen.”

CDC Director Rochelle Walensky said more than 4.1 million adolescents 12 to 17 have been vaccinated so far, including over half a million 12-15-year-olds who have lined up to get a shot since the Pfizer vaccine was authorized for adolescents earlier this month.

Walensky has also shared her family’s personal plight with the virus in urging more Americans to get the shot.

In a hearing on COVID-19 on Capitol Hill last week, Walensky was forced to defend the agency’s integrity against questions about recent murky messaging and shared a personal story about her son to support the CDC guidance on summer camps.

“I want our kids back in camp,” Walensky said, describing how her teenage son counts down the days to his summer camp. “Every year, he comes home from camp and he writes the number of days until he returns to camp the next year. This year, it got to zero and I told him he wasn’t going.”

“We now have 38,000 new infections, on average, per day. Last May 11th, it was 24,000. And we sent a lot of kids home and camps were closed. The camp guidance is intended to get our kids to camp and allow them to stay there,” she continued.

In the same hearing, while acknowledging some parents may not want to be first in line, Walensky she would encourage all parents to get their children vaccinated and encourage children to ask their parents for the vaccine.

“I have a 16-year-old myself and I can tell you he wanted to get the vaccine. He wants his life back,” she told lawmakers.

Walensky declined to give a timeline on Tuesday on when the CDC will release new guidance for schools after publishing information over the weekend suggesting schools should not keep masking policies in place until the end of this school year. When asked why CDC posted new guidance telling fully vaccinated individuals they can go without masks before updating guidance for schools, businesses, and travel, Walensky said they’re working “diligently” on it.

As for the president, whose own life has been marked by family tragedies, Biden has often referenced his own losses in relating to Americans dealing with the pandemic’s hardships.

“I know all too well. I know what it’s like to not be there when it happens,” Biden said back in February to mark 500,000 American lives lost. ‘I know what it’s like when you are there, holding their hands, as they look in your eye and they slip away. That black hole in your chest, you feel like you’re being sucked into it.”

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