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With the Covid-19 vaccine in short supply, hospital pharmacists found themselves in the unexpected position of throwing away one in every six doses of the first Pfizer-BioNTech vaccines distributed this week in the United States.

The confusion came over labeling: The vaccine comes in vials labeled as containing enough for five doses. But pharmacists discovered that, after thawing and mixing the contents with a diluent, each vial contained enough vaccine for six doses. Without explicit approval from the manufacturer, that final dose had to be discarded.


“It was overtly clear early on there’s some extra volume,” said Russell Findlay, pharmacy manager at University of Utah Health. His colleagues called Pfizer on Tuesday to ask if they could use the extra dose, said Findlay, but the company wouldn’t give a definitive answer.

Pharmacists and executives at several health care systems said they didn’t feel they could risk using the extra dose, especially as Pfizer’s vaccine requires two doses, 21 days apart, to be effective. “We’re not fully confident of our future supply. Let’s say we use the six but we get fewer doses in the future, we might not have enough for the second dose,” said Findlay. “We need to be very cautious in managing that supply.”

Across the country in Boston, Paul Biddinger, medical director for emergency preparedness at Mass General Brigham, said he’d heard of the extra doses from the British vaccine rollout earlier this month. Despite being prepared, his team still had to throw out the additional doses on the first day of distribution.


In Texas, the extra doses were discarded on the first day of distribution but, by Wednesday morning, Houston Methodist Hospital chief executive Roberta Schwartz said her team heard from Pfizer that it was okay to use what’s in the vial.

Finally, on Wednesday afternoon, the U.S. Food and Drug Administration updated its guidance, saying health care providers should feel free to use all the full doses within each vial. “At this time, given the public health emergency, FDA is advising that it is acceptable to use every full dose obtainable (the sixth, or possibly even a seventh) from each vial, pending resolution of the issue,” spokesperson Abigail Capobianco wrote in an email to STAT. But any spare half doses should not be combined with half doses from other vials to create a whole one, she added.

But Pfizer was less definitive. Each vial contains enough vaccine for at least five doses, spokesperson Sharon Castillo said in an email to STAT, and each dose must contain 0.3ml. “The amount of vaccine remaining in the multidose vial after removal of 5 doses can vary, depending on the type of needles and syringes used,” she wrote.  ”At this time, we cannot provide a recommendation on the use of the remaining amount of vaccine from each vial. Vaccinators need to consult their institution’s policies for the use of multidose vials.”

If the dosing confusion was raised in the U.K., the FDA and Pfizer ideally should have issued clearer instructions about using the extra dose before distribution began this week in the U.S., said John Grabenstein, adviser to the American Pharmacists Association. “In a situation of limited supply, any waste is unfortunate.”

But all injectable medicines have overfill, he said, and the first stages of clinical practice normally raise small issues. “There’s a thousand matters to address in the first week. This one might only now rise to the level of getting checked out,” he said.

It makes sense to have some left-over liquid in a vial, said Findlay. Slight variations in the syringes used by different health systems could have small effects on the size of each dose, and changes in air pressure at different altitudes could also affect the volume of vaccine in a vial.

Even with the confusion over dosing, the first day of administering vaccines was a success, he said: “Yesterday was the best day of work I’ve ever had.”

  • As a pharmacist I recognize there could be overfill but are the directions correct for adding 1.8 mls of NS? Is the final concentration of vaccine once mixed correct? I haven’t mixed it myself but from what I’m hearing on the media they make it sound like the amounts of final product vary from 5 to 7 shots but that would have to mean the concentrations are off on some of these shots. Is my thinking on this mistaken?

    • The concentration is the same in each vial. Pfizer intended for overfill to ensure 5 full doses despite the size needle used. For every dose withdrawn, you will lose volume in the needle. Depending on needle size, the amount lost varies. This is why it is crucial for the vaccinator to withdraw the volume from the needle into the syringe if your practice is to switch needles prior to injection.

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