Pfizer Inc. filed with U.S. regulators for an emergency-use authorization for its Covid-19 vaccine, seeking clearance for an experimental shot that’s expected to play an important role in an immunization effort to halt the virus.

The vaccine, developed by the U.S. drugmaker with its German partner
BioNTech SE, is the first to seek authorization from the Food and Drug Administration. An emergency clearance would allow Americans to access the vaccine before it’s granted full approval. It is likely to be the first to be made available on a limited basis to health workers and older Americans.

Earlier this week, Pfizer said its experimental vaccine — which relies on messenger RNA technology never before used in an approved medicine — was 95% effective, protecting people of all ages and ethnicities from developing symptomatic Covid-19. So far, there have been no significant safety problems in the trial that includes nearly 44,000 participants.

The FDA is expected to spend the next few weeks reviewing the data, and the vaccine could be available by the middle to the end of December. A key step along the way is a meeting of outside FDA advisers, all experts in infectious diseases and vaccines. They’re set to confer Dec. 10, the FDA said on Friday, allowing the clinical trial data to be vetted in public to bolster confidence.

“Today we were able to submit a very robust data set that we believe meets and, in many cases, exceeds the FDA’s high standards,” Pfizer Chief Executive Officer Albert Bourla said in a video statement announcing the filing.

It took just 248 days from when Pfizer announced the collaboration with BioNTech to approach U.S. regulators for an emergency-use authorization, he said.

Read More: Pfizer Covid-19 Vaccine Faces Hurdles After FDA Filing Friday

Among the vaccine front-runners, the Pfizer-BioNTech project is the only one that didn’t take funding from the White House-led Operation Warp Speed program to accelerate development, manufacturing and distribution of Covid-19 shots. However, the two companies have secured a $2 billion deal to supply 100 million doses to the U.S., with an option for 500 million more.

Pfizer shares closed up 1.4% to $36.70 in New York trading. BioNTech’s U.S. depositary receipts gained 9.1% to $104.07.

Pfizer already has started rolling submissions for the vaccine in Australia, Canada, Europe, Japan and the U.K. and plans “to submit immediately to other regulatory authorities around the world,” Bourla said in the video statement.

Cases Surging

The filing for regulatory clearance comes at a time when the U.S. — which has the world’s largest number of cases at more than 11 million — is fighting a fierce resurgence of infections. A string of promising developments on the vaccine front, however, is offering hope that the virus can be defeated in 2021.

Moderna Inc.’s rival shot appears equally effective, judging from data published on Monday. The Cambridge-based biotech said at the time that it expects to be able to apply for emergency authorization in the U.S. within weeks. A third contender, from
AstraZeneca Plc and the
University of Oxford, is expected to release late-stage trial results in coming days.

Read More: Vaccine Breakthroughs Put Covid Protection Within Reach

In the meantime, public-health officials led by Anthony Fauci, the head of the National Institute of Allergy and Infectious Diseases, have warned it will take months before vaccinations will slow the virus. He and others have urged the continued use of masks and social distancing to slow Covid-19’s advance until the country can hit a level of vaccination that stops the virus.

Both Pfizer’s vaccine and Moderna’s use mRNA technology which essentially teaches the body’s cells to become vaccine factories, allowing the technology to be developed much faster than a traditional shot.

Well-Tolerated

Most people who received the Pfizer-BioNTech regimen tolerated it well, according to an analysis by the companies. The vaccine’s efficacy in people older than 65 was more than 94%, the companies said.

Pfizer has found itself drawn into a contentious political debate about how quickly regulators in the U.S. should allow a vaccine to be given to Americans. While U.S. President Donald Trump pushed to have a shot approved before Election Day, regulators put in place rigorous standards — including two months of safety data — that largely pushed that goal out of reach.

Pfizer’s Bourla said on Friday in an interview with Time that he expects the two-dose regimen to be granted a full approval by the end of the first quarter or early in the second quarter of 2021.

(Updates with FDA review plans in the fourth paragraph.)