University of Miami pediatrician Judith L. Schaechter gives an HPV vaccination to a 13-year-old girl last week in Miami. Joe Raedle/Getty Images hide caption

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A nurse vaccinates a child against pneumonia at a healthcare center in Managua in January. Nicaragua received pneumococcal vaccines from the GAVI Alliance. ELMER MARTINEZ/AFP/Getty Images hide caption

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Construction at the new Nemours Children's Hospital, at the medical city at Lake Nona, Fla., in late 2010. Joe Burbank/Orlando Sentinel hide caption

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High school student Connor Sheehan (No. 44) decided to play in a playoff game, despite having just completed rehab for a sprained ankle. Research suggests that, compared with adults, teens value rewards more than consequences. Kitra Cahana/National Geographic hide caption

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Experts disagree about whether girls as young as 11 should get the HPV vaccine. Mike Kemp/iStockphoto.com hide caption

itoggle caption Mike Kemp/iStockphoto.com