A teen gets a dose of Pfizer's COVID-19 vaccine last month at Holtz Children's Hospital in Miami. Nearly 7 million U.S. teens and preteens (ages 12 through 17) have received at least one dose of a COVID-19 vaccine so far, the CDC says. Eva Marie Uzcategui/Bloomberg via Getty Images hide caption
Scientists once compared the abilities of humans versus canines in tracking a trail of chocolate essential oil laid down in an open field. Though the humans weren't nearly as proficient as the dogs, they did get better with practice. Vladimir Godnik/Getty Images/fStop hide caption
Southern Californians celebrate at a mass vaccination site in Disneyland's parking lot in January. CDC head Dr. Rochelle Walensky cautions that for strongest immunity, recipients get both doses of the Pfizer or of the Moderna vaccine according to schedule. Mario Tama/Getty Images hide caption
Staff and residents of the Ararat Nursing Facility in the Mission Hills neighborhood of Los Angeles got COVID-19 shots on Jan. 7. Coronavirus cases, hospitalizations and deaths have been surging throughout Los Angeles County. Mario Tama/Getty Images hide caption
Pfizer-BioNTech's COVID-19 vaccine has been tested for safety and efficacy in more than 44,000 people. Still, stopping viral spread will take more than immunizations, says the CDC. The agency is calling for those who are vaccinated to continue wearing masks and practicing safe physical distancing. Frank Augstein/AP hide caption
A new study from the New England Journal of Medicine finds that motor vehicle crashes were one of the leading causes of death among children and adolescents in the U.S. in 2016. Tim Graham/Getty Images hide caption
A migrant receives medical attention at a former paper factory in Greece that has been turned into a makeshift camp. Menelaos Michalatos/SOPA Images/LightRocket via Getty Images hide caption
The elaborate Alnwick Garden in northeast England includes a "Poison Garden" that showcases plants with killer properties. Visitors are invited to look but not touch or even smell. Joanne Silberner for NPR hide caption
Patient and counselor: In a village near Bhopal, India, a woman with depression (left) meets with her counselor. The counselor, who lives nearby and speaks the same dialect, has received three weeks of intensive training. The patient says the counselor changed her life for the better. Joanne Silberner for NPR hide caption
High school students in Tanzania gather in a Mental Health Listening Club — first comes the soap opera, then the chance to ask questions about topics like depression. Omar Dabaghi-Pacheco for Farm Radio International hide caption