‘By not slaying the beast, we’re letting it grow stronger’: COVID-19 vaccine hesitancy complicates attempts at herd immunity Jackson Healy , Contributing Writer|April 25, 2021 FILE – In this April 5, 2021, file photo, Leanne Montenegro, 21, covers her eyes as she doesn’t like the sight of needles, while she receives the Pfizer COVID-19 vaccine at a FEMA vaccination center at Miami Dade College in Miami. In the U.S, meanwhile, more than one-fourth of the population — nearly 90 million people — has been fully vaccinated and supplies are so robust that some states are turning down planned shipments from the federal government. (AP Photo/Lynne Sladky, File)