The vaccines for COVID-19 are highly effective, but people can get infected in what appear to be extremely rare cases. The Centers for Disease Control and Prevention has decided only to investigate the cases that result in hospitalization or death. Image Point FR/NIH/NIAID/BSIP/Universal Images Group via Getty Images hide caption
Wearing a mask and a face shield to curb the spread of the coronavirus, 10-year-old Jade Chan Puc writes in her workbook during the first day of class in Hecelchakán, Campeche state, Mexico, on April 19. On average, schools in Latin America and the Caribbean were closed longer than any in any other region, according to UNICEF. Martin Zetina/AP hide caption
Serious cases of COVID-19 have grown in recent weeks in Americans 50 and younger. Tempura/Getty Images hide caption
A coffin is buried at the Vila Formosa cemetery in Sao Paulo, Brazil, late last month. Brazil has been experiencing record numbers of coronavirus infections and COVID-19 deaths in recent weeks. Miguel Schincariol/AFP via Getty Images hide caption
A person receives a COVID-19 shot in Federal Way, Wash., at a vaccination clinic for the Pacific Islander Community Association of Washington held on Feb. 4. David Ryder/Getty Images hide caption
People line up for drive-through COVID-19 vaccination at Coors Field baseball stadium in Denver on Saturday. Chet Strange/AFP via Getty Images hide caption
The Florida Department of Health said officials are working alongside the Centers for Disease Control and Prevention to figure out how a 20-something-year-old man contracted the new, more contagious coronavirus strain that was first discovered in the U.K. Lynne Sladky/AP hide caption
A laboratory technician is pictured handling swab samples at a hospital in Mulhouse, France, in November. French officials confirmed the country's first case of the new coronavirus variant on Friday. Patrick Hertzog/AFP via Getty Images hide caption