C.D.C. Tells States How to Prepare for Covid-19 Vaccine by Early November

That’s a positive development, “so it doesn’t just all wind up in high-income, affluent suburbs,” said Dr. Cedric Dark, an emergency medicine physician at Baylor College of Medicine in Texas.

The C.D.C. noted in its guidance that “limited Covid -19 vaccine doses may be available by early November 2020.” The documents were dispatched the same day that Dr. Robert Redfield, director of the C.D.C., sent a letter to governors asking them to ready vaccine distribution sites by Nov. 1, as McClatchy reported.

The agency also said its plans were as yet hypothetical, noting, “The Covid-19 vaccine landscape is evolving and uncertain, and these scenarios may evolve as more information is available.” A C.D.C. spokeswoman confirmed that the documents were sent but declined to comment further.

Many of the details listed for the two vaccines — including required storage temperature, the number of days needed between doses, and the type of medical center that can accommodate the product’s storage — match what Pfizer and Moderna have said about their products, which are based on so-called mRNA technology. Neither company responded to requests for comment.

The scenarios, which assume that the two vaccines could demonstrate sufficient safety and effectiveness for an emergency authorization from the F.D.A. by the end of October, note that Vaccine A, which seems to match Pfizer’s, would have about two million doses ready within this time frame, and that Vaccine B, whose description matches Moderna’s, would have about one million doses ready, with tens of millions of doses of each vaccine ready by the end of the year. Although it’s possible that some promising preliminary data may emerge by the end of October, experts are skeptical.

“The timeline that’s reported seems a bit ambitious to me,” Dr. Dark said. “October’s like 30 days away.”

Trials that test a vaccine’s effectiveness can take years to yield reliable results. It’s possible to draw conclusions sooner “if there is an overwhelming effect” in which vaccinated people appear to be far better protected from disease, said Padmini Pillai, a vaccine researcher and immunologist at M.I.T. But data gathered early in a trial might not hold true months down the line. And researchers need time to test large numbers of people from a variety of backgrounds to determine how well the vaccine works in different populations — including the vulnerable communities identified in the guidelines.