Walgreens has inoculated hundreds of thousands of Americans against Covid-19 this year using the vaccine developed by Pfizer and Germany’s BioNTech. But the pharmacy chain has not been following guidance from federal health officials about the timing of second doses. Most other major pharmacies, including CVS and Rite Aid, stuck with the C.D.C.’s guidance on the timing of second doses. CVS, for example, schedules second Pfizer shots for 20 to 23 days after the first shot, said T.J. Crawford, a spokesman for the chain. Some public health experts believe the U.S. should delay the second doses of vaccines by longer than Walgreens has been doing with the Pfizer vaccine.
