Months after contracting COVID-19, seemingly healthy, active, younger people are experiencing what some doctors have started referring to as Post-acute COVID Syndrome. Anderson Cooper explains. Enrollment data from 78 of the country's largest school districts found at least 240,000 students were unaccounted for as school began during the pandemic. Sharyn Alfonsi reports. Four of the eight men and women over the age of 90 -- who were featured in a 2014 60 Minutes story are still alive and participating in the 90+ Study. Lesley Stahl catches up with them on this week's "60 Minutes."

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