A baby receives the rotavirus vaccine during a clinical trial in Niger. The new vaccine is the first designed specifically for children in sub-Saharan Africa. It doesn't require refrigeration and will be cheaper than ones currently available. Krishan Cheyenne/MSF hide caption

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Krishan Cheyenne/MSF

Andie Vaught grasps a stress toy in the shape of a truck as she prepares to have blood drawn as part of a clinical trial for a Zika vaccine at the National Institutes of Health in Bethesda, Md., in November 2016. Allison Shelley/The Washington Post/Getty Images hide caption

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Robert F. Kennedy Jr. in the lobby of Trump Tower in New York, Tuesday, after meeting with President-elect Donald Trump. Kennedy said Trump put him in charge of a commission on "vaccine safety." Evan Vucci/AP hide caption

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Evan Vucci/AP

The mumps virus is on the loose. Cases are popping up in Arkansas, Iowa and Illinois. Alissa Eckert/CDC hide caption

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Alissa Eckert/CDC

Mumps Bump: Cases Rise In Iowa, Illinois And Arkansas

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The HPV vaccine has reduced the prevalence of the cancer-causing human papillomavirus by as much as 65 percent among those who are vaccinated. Matthew Busch for The Washington Post/Getty Images hide caption

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Matthew Busch for The Washington Post/Getty Images

Advice For Doctors Talking To Parents About HPV Vaccine: Make It Brief

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Luz Barajas took her son Carlos Cholico to get his flu shot at Crawford Kids Clinic in Aurora, Colo., last year. Health officials say there is some evidence the flu shot is more protective than the nasal flu vaccine. Brent Lewis/The Denver Post via Getty Images hide caption

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Brent Lewis/The Denver Post via Getty Images

Fourth-grader Jasmine Johnson got a FluMist spray at her Annapolis, Md., elementary school in 2007. This year, the nasal spray vaccine isn't recommended. Susan Biddle/Washington Post/Getty Images hide caption

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Susan Biddle/Washington Post/Getty Images