Gretchen Lee, a third grader in Washington, D.C., was wrapping up her last week in school ahead of Christmas break when the unexpected happen.
Within a matter of hours, a long-planned family trip to Seattle to visit a new baby cousin suddenly evaporated. Her parents' tickets to the new Spider-Man movie went unused. And Gretchen, whose symptoms are mild, is now mostly isolating until her parents can figure out next steps.
"I didn't think that they would have to separate me from my sister," Gretchen said when asked about the worst part of getting COVID just days before Christmas.
It's the Grinch's dirtiest trick yet. If 2020 was the year we all stayed home, 2021 was supposed to be the year of joyous family reunions and travel splurges.
Instead, the nation has logged more than 1.1 million new coronavirus cases in the last week alone. And many of the cases are children, with 170,000 kids testing positive last week.
The Centers for Disease Control and Prevention says any person infected with the virus -- vaccinated or not -- should isolate for 10 days. That means staying alone in a bedroom and, if possible, not sharing a bathroom.
It's a rule that's never been practical for families living in small spaces or with very young children.
It's also one that, during Christmas, seems a particularly cruel twist of fate for conscientious parents and their Santa-loving kids.
"We have done everything that we were supposed to do," said Gretchen's mom, Gloria Lee, who, like her husband, is both vaccinated and boosted.
Dr. Mark Kline, an American pediatrician and infectious diseases specialist working as physician-in-chief and chief medical officer at Children's Hospital New Orleans, said there's no one good answer for how to handle a COVID case in the family.
In lieu of strict isolation, a family could opt for masks in the house, assuming everyone else is fully vaccinated and low medical risk, he said. Upgrading to surgical masks instead of cloth masks is a good idea too. And moving the celebration outdoors or cracking the windows can make it less likely the virus will spread, Kline said.
"These are difficult questions to answer. There's the ideal, and then there is the pragmatic approach. And I think we have to be pragmatists on this," said Kline.
Some doctors and disease experts are questioning whether the 10-day isolation rule still makes sense if people are vaccinated. That's because while a vaccinated person without symptoms can still spread the virus, they probably aren't contagious for as long as an unvaccinated person.
Dr. Amesh Adalja, a senior scholar at Johns Hopkins' Center for Health Security, estimates a vaccinated person's infectious period is about 40% or 50% shorter than the unvaccinated. So, instead of 10 days isolation, they might only need five or six, he said.
"When people get a breakthrough infection, the period of time that they are contagious is truncated, because the immune system jumps into effect very quickly and slams down the viral load," Adalja said.
One tactic for families, Adalja said, could be to keep doing a rapid test on the COVID-positive person until they test negative. Whereas a laboratory PCR test might still pick up tiny pieces of the virus, the benefit of a rapid test is that it is most likely to register positive while a person is truly contagious.
The approach isn't foolproof, and families might need to think twice if anyone has a medical condition that makes them vulnerable to a more serious outcome from COVID. But a truncated isolation period for a vaccinated person is already being pushed by the airlines and some health care workers who say it doesn't make sense to keep vaccinated personnel at home for the full 10 days.
Late Thursday, the CDC relaxed its quarantine and isolation rules slightly for health care workers out of concern that hospitals might face severe staffing shortages next month following the latest wave of omicron cases.
"We have the technology to (avoid) one-size-fits-all isolation periods for everybody. We can use antigen testing to be able to do this," Adalja said. "If the NFL can do it, why can't we?"
As for Gretchen, who is asking in vain for a puppy this Christmas, she isn't too worried about getting sick because she understands the vaccine will protect her.
But her parents say they wouldn't mind more up-to-date guidance from federal health officials on whether a 10-day isolation period makes sense for a vaccinated person and how to navigate testing other vaccinated members of the household.
"There are obvious downsides to not making memories and missing out playing and being social. Those are real harms," said Gretchen's father, Woo Lee.
"But you know, the other side of that is that she could continue to spread this virus," he said, adding, "Our decisions could affect other people."
ABC News' producer Arielle Mitropoulos and Karen Travers contributed to this report.