New York, Dec 17 (IANS): After pharmacists in the US discovered extra doses in the vials of Pfizer's Covid-19 vaccine which has been approved for emergency use in the country, the US Food and Drug Administration (FDA) said that those extra doses can be used.

This means a significant boost to vaccine supply in the country even as Covid-19 cases continue to surge.

"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," the FDA said in a tweet on Wednesday.

Each Pfizer vial is supposed to have five doses of the vaccine.

"However, since the vials are preservative free, it is critical to note that any further remaining product that does not constitute a full dose should not be pooled from multiple vials to create one," the FDA said.

According to a report in Politico, the extra vaccine doses could potentially expand the nation's supply by up to 40 per cent.

A Pfizer spokesperson told USA TODAY that "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."

Pfizer said it cannot provide a recommendation on the use of the remaining amount.

The US FDA gave the emergency use authorisation for Pfizer-BioNTech Covid-19 vaccine last week.

The US started its Covid-19 vaccine rollout nationwide on Monday as the death toll in the pandemic topped 300,000 in the country.