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Helen Down holds her 14-month-old daughter, Amelia, for an MMR shot in Swansea, Wales, April 2013. The vaccination was in response to a measles outbreak. Geoff Caddick/AFP/Getty Images hide caption

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This one's virus-free: Matthew Followill, Nathan Followill and Caleb Followill of Kings of Leon performed in Los Angeles in December. Kevin Winter/Getty Images for Radio.com hide caption

itoggle caption Kevin Winter/Getty Images for Radio.com