A worker stands on top of a storage bin on July 27, 2011, at a drilling operation in Claysville, Pa. The dust is from powder mixed with water for hydraulic fracturing. Keith Srakocic/AP hide caption

itoggle caption Keith Srakocic/AP

A new study from the Centers for Disease Control and Prevention finds no link between the number of vaccinations a young child receives and the risk of developing autism spectrum disorders. Jeff J. Mitchell/Getty Images hide caption

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A microscopic image of prostate cancer. Researchers have found new genetic markers that flag a person's susceptibility to the disease, as well as breast and ovarian cancer. Otis Brawley /National Cancer Institute hide caption

itoggle caption Otis Brawley /National Cancer Institute

Otolaryngologist Sandra Lin uses under-the-tongue drops to treat patients with allergies at Johns Hopkins in Baltimore. Courtesy of Keith Weller/Johns Hopkins Medicine hide caption

itoggle caption Courtesy of Keith Weller/Johns Hopkins Medicine

George McCann has been diagnosed with a subtype of bipolar disorder called the "fear of harm" profile, and finds that a prescribed dose of ketamine every few days alleviates his symptoms. Michael Rubenstein for NPR hide caption

itoggle caption Michael Rubenstein for NPR

A towel covers the face of a man in a geriatric day care facility of the German Red Cross at Villa Albrecht in Berlin. Carsten Koall/Getty Images hide caption

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Robert Monges, a coach for James Lick High School, checks tight end Dominic Brewster for a concussion during a football game played in Morgan Hill, Calif., in 2006. Patrick Tehan/San Jose Mercury News/MCT/Landov hide caption

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Lauren Fant winces as she receives her third and final shot of HPV vaccine from nurse Stephanie Pearson in Marietta, Ga., in 2007. John Amis/AP hide caption

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An electron micrograph of HIV particles infecting a human T cell. French researchers say they've found 14 patients with so little HIV virus in their blood that the patients have gone into "long-term remission." National Institute of Allergy and Infectious Diseases hide caption

itoggle caption National Institute of Allergy and Infectious Diseases

Students at the College of Central Florida in Ocala, Fla., perform CPR on a mock patient. Bruce Ackerman/Ocala Star-Banner /Landov hide caption

itoggle caption Bruce Ackerman/Ocala Star-Banner /Landov

Ten milligram tablets of the prescription drug Adderall. The drug is used to treat ADHD and is used by some students to boost their academic performance. Jb Reed/Bloomberg via Getty Images hide caption

itoggle caption Jb Reed/Bloomberg via Getty Images