NEW YORK — Pfizer, a US-based multinational pharmaceutical corporation, submitted on Friday a request to the US Food and Drug Administration (FDA) for an emergency use authorization for its coronavirus vaccine.

It is not clear how long the FDA will take to study the data. However, the US government expects to approve the vaccine in the first half of December.

Data from an advanced trial showed the vaccine, which requires two doses at a three-week interval, appeared to be 95 percent effective in preventing symptomatic coronavirus.

Pfizer and its German partner BioNTech are expected to have 50 million doses available this year and 1.3 billion in 2021, using facilities both in the US and Belgium.

"Our work to deliver a safe and effective vaccine has never been more urgent, as we continue to see an alarming rise in the number of cases of COVID-19 globally," Dr. Albert Bourla, Pfizer chairman and CEO, said in a news release.

"Filing in the US represents a critical milestone in our journey to deliver a COVID-19 vaccine to the world and we now have a more complete picture of both the efficacy and safety profile of our vaccine, giving us confidence in its potential."

The companies said they have also "initiated rolling submissions" with medical regulators in Europe and the United Kingdom, and that they intend to "submit applications to other regulatory agencies worldwide in the coming days."

One potential stumbling block for the Pfizer vaccine is its requirement of ultracold storage. The shots must be stored at minus 94 degrees Fahrenheit — far colder than standard cooling systems at health care facilities across much of the country. — Agencies