As winter storms threatened to upend distribution of Covid-19 vaccines, the White Home on Tuesday mentioned that states collectively would start receiving 13.5 million doses every week — a bounce of over two million doses due partially to a shift in the best way the federal government is allocating doses of Pfizer’s vaccine. And Jen Psaki, the White Home press secretary, mentioned that a new federal pharmacy program will now present two million weekly doses, a doubling of its preliminary provide.

The will increase had been welcome developments for state officers determined to inoculate extra weak People earlier than more contagious variants of virus change into dominant.

The Biden administration has been working with Pfizer, the maker of 1 federally approved vaccine, to get the corporate extra manufacturing provides, together with pumps and filtration models, via the Defense Production Act. The administration introduced final week that Pfizer and Moderna, the opposite maker of the vaccine approved in the US, will be capable of ship a complete of 400 million doses by the top of Might, effectively forward of schedule.

The newest enhance in provide got here partly as a result of Pfizer, as of this week, is getting credit score for six doses as a substitute of 5 doses per vial, a White Home spokesman mentioned. Two-thirds of the enhance was because of elevated output, the spokesman mentioned. Officers now say there may be an ample provide of specialised syringes wanted to extract the additional Pfizer dose. The White Home warned state officers final week that due to that accounting change, the variety of doses that the federal authorities mentioned it had delivered would shoot up, even when the quantity of vaccine in every vial itself didn’t.

Ms. Psaki informed reporters on Tuesday that with the newest improve, vaccine deliveries had jumped 57 p.c since President Biden was inaugurated. Administration officers have usually framed these will increase as Mr. Biden’s accomplishment, although, at the least to some extent, the provides had been anticipated to develop as Pfizer and Moderna ramped up manufacturing.

The announcement on Tuesday got here as winter storms within the South continued to disrupt vaccine distribution. Clinics had been closed and shipments had been stalled in states the place the tempo of vaccinations already had lagged behind the nationwide common. Vaccine appointments had been rescheduled or canceled from Texas to Kentucky.

A spokeswoman for the Facilities for Illness Management and Prevention mentioned Tuesday that the federal government was projecting “widespread delays” in vaccine shipments and deliveries within the coming days, as climate was affecting a FedEx facility in Memphis and a UPS facility in Louisville, each vaccine transport hubs.

“C.D.C. and federal companions are working intently with the jurisdictions, in addition to manufacturing and transport companions, to evaluate climate situations and assist mitigate potential supply delays and cancellations,” the spokeswoman mentioned.

Ms. Psaki mentioned that officers had been monitoring the storms and in contact with state and native governments. She mentioned there was a “contingency plan to make sure individuals are getting the doses they want at an acceptable timeline.”

The rise in doses for pharmacies introduced on Tuesday got here after White Home officers had warned that provides to that program could be extraordinarily restricted at first. Greater than 40,000 pharmacies are anticipated to obtain doses as a part of this system.

On Tuesday, Dr. Anthony S. Fauci, the nation’s prime infectious illness skilled and adviser to Mr. Biden, revised his personal estimate from final week, when he predicted the start of an “open season” by April. “That timeline will most likely be extended, possibly into mid-to-late Might and early June,” he mentioned in an interview with CNN.

Campbell Robertson contributed reporting.