Vaccination

U.S. Could Vaccinate a Fifth of Americans in a Bird Flu Emergency

• Two clinical trials of the vaccine likely to be used, under way since last year, have yet to produce data.
• The strain of avian flu known as H5N1 has been circulating among birds in the U.S. since late 2021.
• It is known only to have infected two people in the country, including a Texas dairy worker last month.