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Moderna wants to add doses to its vials to speed COVID-19 vaccinations

The space at the top of each container could hold more vaccine, if the FDA approves

Nurse Samantha Schuko prepares a dose of the Moderna vaccine at Gillette Stadium in Foxborough.
Nurse Samantha Schuko prepares a dose of the Moderna vaccine at Gillette Stadium in Foxborough.Jessica Rinaldi/Globe Staff

Samantha Schuko never gave much thought to the little space above the liquid in each vial of Moderna’s COVID-19 vaccine.

The registered nurse said she simply takes a syringe containing half a milliliter of vaccine previously drawn by a co-worker from the vial and injects it into a shoulder. After 10 shots, the bottle is empty.

That space, however, is the focus of discussions between the Cambridge biotech and the Food and Drug Administration. Moderna has asked regulators to let it fill the gap with five more doses to help accelerate the vaccine rollout.

“That would be awesome,” said Schuko, 31, who estimated she has given at least 100 shots a day of Moderna’s vaccine since a vaccination site opened Jan. 18 at Gillette Stadium in Foxborough. Anything that increases the ability to vaccinate would just be amazing.”

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As Moderna approaches its daily production benchmark of 1 million doses, the company’s president, Stephen Hoge, wants to increase the contents of each vial to 15 doses to relieve “one of the manufacturing bottlenecks,” according to a recent statement by a spokeswoman.

“One of the capacity constraints beyond the amount of drug product available is how many vials you can fill in a given time,” the statement said.

The discussions about increasing the number of doses in a vial illustrates how seemingly mundane details of the vaccination program can have far-reaching implications.

Moderna developed and manufactures the messenger RNA vaccine, which was cleared for emergency use in December a week after the FDA authorized the first vaccine, by Pfizer-BioNTech. Catalent, a New Jersey contractor, fills each Moderna vial with 10 doses at a factory in Bloomington, Ind. If Moderna is approaching a million daily doses, that means Catalent “fills and finishes” roughly 100,000 vials a day.

When drug companies make vaccines, the substance goes in vials that typically contain one to 20 doses, according to Prashant Yadav, who studies health care supply chains with the nonprofit Center for Global Development in Washington, D.C.

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Moderna opted to fill each vial with 10 doses instead of 15 because it was concerned that health care workers might have to throw away extra doses if not enough people showed up to get shots.

The vaccine, which is shipped to states frozen and then thawed before vaccination, has to be discarded six hours after the first dose is drawn from the vial, under FDA guidelines issued when the agency cleared it for emergency use on Dec. 18. It cannot be refrozen.

But with demand for the vaccine far outstripping supply, Moderna has concluded it’s unlikely it would have to discard doses if the vials contained 15 shots, particularly at mass vaccinations sites such as Gillette.

Yadav suspects that Catalent could easily reprogram its automated equipment to accommodate 15 doses, or 50 percent more.

But other questions would need to be considered: Would the vials be more likely to allow bacteria to enter if workers dispensing vaccines pierced the rubber stopper 15 times instead of 10? Would filling the space with five more doses make each vial ― a plastic container with a thin glass coating produced by the Alabama company Si02 Materials Science ― more likely to break? Would Moderna be better off switching to a slightly larger vial and leaving extra room again? If so, what implications would that have for the boxes containing 10 vials that Moderna uses to ship the vaccine?

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“Increasing capacity is not just solving one bottleneck,” Yadav said. “When you solve one bottleneck, then [the constraint] shifts to something else.”

The FDA has shown a willingness to increase doses. In December, it said a sixth or even seventh dose that health care workers were able to draw out of the vial of Pfizer-BioNTech’s vaccine could be used after news reports said pharmacists were throwing excess vaccine away because the vials were labeled as containing five doses.

An spokeswoman said the FDA could not comment on Moderna’s proposal and referred all questions to the company.

Ray Jordan, a spokesman for Moderna, gave no timetable for when the FDA might allow the company to increase the number of doses, but he was encouraged the agency was considering it. “It’s an ongoing discussion with the FDA,” he said.



Jonathan Saltzman can be reached at jonathan.saltzman@globe.com.