Two polio cases have been reported in Ukraine, where some parents are fearful of vaccinations. Above: A child receives the diphtheria, whooping cough and tetanus vaccine in a children's hospital in Kiev. Sergei Chuzavkov/AP hide caption

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A woman receives the rVSV-ZEBOV Ebola vaccine at a clinical trial in Conakry, Guinea. The vaccine appears effective after only one shot. Cellou Binani/AFP/Getty Images hide caption

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Ebola Vaccine Hailed As 'Game Changer' In Fight Against The Virus
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A baby helps make history. The Kenyan child is receiving the new malaria vaccine — the first ever that can wipe out a parasite — as part of a clinical trial. Karel Prinsloo/AP hide caption

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Why A Vaccine That Works Only A Third Of The Time Is Still A Good Deal
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This did not really happen. Cows' heads did not emerge from the bodies of people newly inoculated against smallpox. But fear of the vaccine was so widespread that it prompted British satirist James Gillray to create this spoof in 1802. H. Humphrey/Henry Barton Jacobs Collection, Institute of the History of Medicine, JHU hide caption

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A Cow Head Will Not Erupt From Your Body If You Get A Smallpox Vaccine
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Vikram is the first child to wear a Khushi Baby necklace, which will keep track of his immunizations. He's at a vaccine clinic in Rajasthan, India. Ruchit Nagar/Courtesy of Khushi Baby hide caption

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Which flu vaccine should you get? That may depend on your age and your general health. Joe Raedle/Getty Images hide caption

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Flu Season Brings Stronger Vaccines And Revised Advice
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Proteins and enzymes that will produce antibodies for the experimental Ebola drug ZMapp are developed on the leaves of the nicotiana benthamiana plant, a relative of tobacco. Here, indicator proteins glow under ultraviolet light — a way to assess the success of bacteria spread. Sean Gallup/Getty Images hide caption

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A health worker administers the malaria vaccine at a clinical trial in Kilifi, Kenya. Joseph Okanga/Reuters /Landov hide caption

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First Malaria Vaccine Moves A Step Closer To Approval
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Kimberly Delp gives a flu shot to Carleen Matthews at the Homewood Senior Center in Pittsburgh, Pa., last September. Andrew Rush/AP hide caption

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