US health officials call for booster shots against COVID-19

In this July 22, 2021, file photo, health care worker fills a syringe with the Pfizer COVID-19 vaccine at the American Museum of Natural History in New York. U.S. health officials Wednesday, Aug. 18, recommended all Americans get COVID-19 booster shots to shore up their protection amid the surging delta variant and evidence that the vaccines' effectiveness is falling. (AP Photo/Mary Altaffer, File)