Pipettes containing immune cells for testing against possible flu vaccines are seen in the Vaccine Research Center at the National Institutes of Health, Tuesday, Dec. 19, 2017, in Bethesda, Md. (AP Photo/Carolyn Kaster)
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Pipettes containing immune cells for testing against possible flu vaccines are seen in the Vaccine Research Center at the National Institutes of Health, Tuesday, Dec. 19, 2017, in Bethesda, Md. (AP Photo/Carolyn Kaster)
