Walgreens’s system currently allows people to rebook their second-dose appointment, but they can do so only the day before the appointment.
“I’m not happy about it,” Ms. DeTurris Poust said. “It gives me one extra week of not being protected, so it means there’s one more week that I’m worried about catching it from someone, or giving it to someone.”
Some public health experts said they were not concerned that Walgreens has been scheduling doses with a four-week gap.
“It’s a week difference. Everybody’s going to need to put it in their contexts and their risk factors, but I think this is a very reasonable approach” from Walgreens, said Dr. Katherine Poehling, a pediatrician at Wake Forest School of Medicine who sits on the C.D.C. advisory panel that recommended that Pfizer doses be given roughly three weeks apart.
But other experts said they were troubled.
“It is not the role of a private, for-profit company to make public health decisions that should be determined by guidelines issued by a public health authority,” said Lawrence Gostin, a global health law professor at Georgetown University.
Dima Qato, a pharmacist and associate professor at the University of Southern California School of Pharmacy, said she was concerned about how the public perceives inconsistent messages about spacing doses of the same vaccine.
“As we’re trying to build trust in this pandemic, I think this may push us back,” Dr. Qato said.
Walgreens is not the only vaccine provider that has been giving second shots slightly later than recommended. Others around the country have been doing so for months, especially in the early days of the rollout when vaccine supply was constrained and sites had little clarity about which vaccines and how many doses they would be receiving in subsequent weeks, said Tinglong Dai, who studies health care operations at Johns Hopkins University.