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 simple switch of ingredients made a big difference in how mice responded to experimental cancer vaccines. Andrei Tchernov/iStockphoto.com hide caption

itoggle caption Andrei Tchernov/iStockphoto.com

Nurse Christel Petersen inoculates a child in the South African Tuberculosis Vaccine Initiative study in 2011. Rodger Bosch/AFP/Getty Images hide caption

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The fall armyworm, a corn pest, is now also a vaccine factory. Wikimedia Commons hide caption

itoggle caption Wikimedia Commons

When flu viruses (in red) accumulate an escape protein too quickly, they exit the cell nucleus (in blue) before they've made enough viral copies to spread the infection. Benjamin tenOever hide caption

itoggle caption Benjamin tenOever

Some parents have worried that kids get too many vaccinations too quickly. A review of all the available research suggests those concerns are misplaced. Dmitry Naumov/iStockphoto.com hide caption

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A boy in Lima, Peru, receives a hepatitis B vaccine during an immunization drive in 2008. The United Nations is considering a ban on the preservative thimerosal, which is often used in hepatitis B and other vaccines in developing countries. Martin Mejia/AP hide caption

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Does a little sugar water before shots really help ease a babies' pain? If only they could tell us. Dmitry Naumov/iStockphoto.com hide caption

itoggle caption Dmitry Naumov/iStockphoto.com

At a Los Angeles media briefing in 2010, Mariah Bianchi describes how her own case of whooping cough caused the death of her newborn son. Reed Saxon/AP hide caption

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A mother dresses her baby after doctors examined him during the malaria vaccine trial at the Walter Reed Project Research Center in Kombewa in Western Kenya in October 2009. Karel Prinsloo/AP hide caption

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Two boys study together at a Chicago yeshiva in 2009. Public health officials say this type of close physical contact caused a mumps outbreak to spread throughout several orthodox Jewish communities in and around New York City. M. Spencer Green/AP hide caption

itoggle caption M. Spencer Green/AP