The following article originally appeared in FiercePharma and was written by Arlene Weintraub

Why did healthcare workers in California and Alabama have to return trays of Pfizer’s COVID-19 vaccine after discovering they were stored at temperatures that were colder than recommended? Does each vial of the vaccine contain more than the expected five doses, and if so, can those be used to meet the high demand for the shot?

Those were some of the questions U.S. government officials addressed yesterday. Operation Warp Speed co-leader Gen. Gustave Perna kicked off a press conference citing “an excellent collaboration” between the government and Pfizer, but when asked for additional details, he and other leaders of Operation Warp Speed hinted that the effort to speed the vaccine to vulnerable populations may not be going as smoothly as advertised.

During the press event, Health and Human Services Secretary Alex Azar acknowledged, with some frustration, that Pfizer is facing some production hurdles with its mRNA vaccine. “We have recently been informed by them, finally, of various challenges that they might have in their manufacturing and we will ensure that by whatever mechanism, that we provide them full support to ensure that they can produce for the American people,” Azar said.

Azar did not provide details about what Pfizer’s challenges have been. Pfizer did not immediately respond to a request for comment from Fierce Pharma. But CEO Albert Bourla, Ph.D., has been quite vocal recently about one major issue the company is facing.

Bourla said during an interview on CNBC Monday that Pfizer is negotiating with the U.S. government to double the original order for 100 million doses and to provide the additional vaccine in the first half of next year. But Pfizer can only make good on that promise if raw materials suppliers prioritize the company’s orders.

Pfizer is “running at critical supply limitations,” Bourla said, adding that he hopes the government deploys the Defense Production Act to solve the problem.

During the Wednesday press conference, Azar expressed confidence the government would be able to strike a deal for additional Pfizer doses to be delivered in the second quarter. “We are working with them to provide them whatever assistance, now that they have identified some of the production challenges,” he said.

But Azar also scolded Pfizer for not engaging with the federal government as closely as other vaccine developers have during the development process.

“It’s important to understand that the Pfizer relationship, while it is very much a part of Operation Warp Speed, is a different contractual relationship than the other five vaccine manufacturers” that are in late-stage clinical trials, Azar said. Those other companies, which include mRNA vaccine maker Moderna, “are more intimately engaged in the support of the development and manufacturing of their product on an ongoing basis, whereas the relationship that Pfizer wanted with Operation Warp Speed was the guaranteed purchase of vaccine.”

Therefore, Azar added, the government has had less visibility into the challenges Pfizer is facing. “And so part of our ongoing discussions is to remediate that,” he said.

Azar’s comments came in the wake of reports suggesting the government has been more focused on speeding raw materials to Moderna and other vaccine makers that did take federal funding for R&D. Plus, Pfizer board member Scott Gottlieb, M.D., touched off a public dispute with HHS last week when he reported that the government had turned down multiple offers for more COVID-19 vaccine doses, even as recently as November.

Meanwhile, a separate issue with Pfizer’s vaccine emerged Wednesday, prompting the FDA to reach out to the company. Some pharmacists administering the shots noticed that each vial contained more than the expected five doses, according to several press reports. They wondered whether they could use the leftovers to eke out an additional dose, or even two.

The FDA responded on Twitter Wednesday night, saying that “given the public health emergency, FDA is advising that it is acceptable to use every full dose obtainable… from each vial, pending resolution of the issue.” The agency added that it is working with Pfizer to determine how best to handle the leftover vaccine.

As for those vaccine doses stored at too-cold temperatures, Warp Speed is now working with the FDA and Centers for Disease Control “to determine if that anomaly is safe or not. We were taking no chances,” Perna said.