By Jared S. Hopkins

Pfizer Inc. said it plans to ask U.S. health regulators on Friday to permit use of its Covid-19 vaccine, a milepost in months of frantic efforts to find a medicine that could beat back a rampaging pandemic.

Once the company files, it would be up to the U.S. Food and Drug Administration to decide whether the two-shot vaccine works safely enough to roll out to millions of people.

It is unclear how long the agency will take to review the vaccine, which Pfizer and partner BioNTech SE just days earlier said was 95% effective and well-tolerated in a 44,000-subject trial.

Given the urgency, the FDA is expected to move quickly. The timing of the filing is in line with industry and government officials' projections for authorization and distribution to begin next month. Pfizer said the filing could allow for distribution to begin by the middle to end of December.

A green light would cap the fastest vaccine development program ever in the West, going from laboratory to authorization in less than a year. Pfizer, which partnered with Germany's BioNTech in March, has so far spent about $2 billion on the effort.

Then companies, health authorities and physicians would face more daunting tasks: making enough shots to meet demand, distributing them and convincing people to take them.

Health authorities say vaccines, and the protection they provide if enough people receive injections, will be key to allowing people to return to schools, workplaces and other establishments.

Vaccines developed in Russia and China are already in use, though their testing is ongoing. Neither the U.S. nor Europe has allowed a Covid-19 vaccine to go into distribution.

Pfizer's submission for authorization follows the collection of two months of safety data on about 19,000 study subjects, as the FDA required.

Pfizer and BioNTech said Wednesday that 162 of the 170 subjects in a large trial who developed Covid-19 with at least one symptom had received a placebo, indicating the vaccine was 95% effective at protecting against Covid-19.

The vaccine also showed to be effective at protecting against severe Covid-19, as nine out of the 10 severe cases that surfaced in the trial were volunteers who took a placebo.

Moderna Inc. has reported similarly positive pivotal-trial data for its vaccine and is expected to seek FDA authorization in the next few weeks, after it finishes collecting all of its vaccine's safety data.

Vaccines from AstraZeneca PLC and Johnson & Johnson are further behind in late-stage, or Phase 3, testing. Novavax Inc. said it would begin its Phase 3 trial in the U.S. this month.

Successful vaccines usually take at least a decade to develop, according to a 2013 study in the journal PLOS One. Many falter in testing.

Like Moderna's vaccine, Pfizer and BioNTech's shot uses a gene-based technology that has long promised faster development, but has never before produced a product sanctioned by regulators.

Their messenger RNA vaccines ready a person's immune system to protect against Covid-19 by training cells to make molecules that wage battle against the new coronavirus.

Pfizer is seeking what is known as an authorization for emergency use, a kind of interim clearance the FDA grants during pandemics to speed up the use of urgently needed medicines.

While the authorization is granted faster than a full approval, the FDA has said it plans to hold the shots to similarly rigorous standards given how millions of healthy people will be injected.

As part of its review, FDA scientists are expected to look at data from individual study subjects such as for signs of any troubling side effects.

An independent panel of doctors and other vaccine experts will meet, likely in early December, to review data on the shot and advise the agency.

The advisory panel is expected to consider whether the vaccine was shown to work safely in certain racial, ethnic and age groups, and give a recommendation whether the vaccine should be authorized and for whom.

The FDA could authorize the vaccine broadly for the U.S. population or limit it to specific groups, such as the elderly or minorities.

The vaccine showed to be more than 94% effective in adults over 65 years old, Pfizer and BioNTech said. More than 40% of the subjects in its large trial includes ethnic and minority groups.

Researchers enrolled nearly 44,000 volunteers in the study, which started in late July, to increase the odds that some would develop Covid-19 with at least one symptom, though only a fraction were needed to assess whether the shot works safely.

Standard statistical methods, used in most previous vaccine trials, allow relying on such a small number of sickened volunteers to assess the shots.

If the vaccine is authorized, Pfizer, health authorities and physicians will then face the arduous tasks of making enough shots to meet demand, distributing them and convincing individuals to take the vaccine.

Initial supplies will be limited, enough for 25 million people world-wide this year, half of them in the U.S., according to the companies.

By the end of next year, Pfizer and BioNTech expect to make 1.3 billion doses, which would inoculate half as many people because each person needs to take two doses three weeks apart.

Federal, state and local health officials have been devising plans for how the supplies will be divvied up and who should get them first.

Health experts advising the U.S. government have recommended health-care workers treating Covid-19 patients be first, followed by those at high risk of infection like elderly in nursing homes and prisoners.

The general public probably wouldn't get access until the spring or summer, according to federal health officials.

Pfizer has set up its own system in the U.S. and certain other countries for distributing the shots.

The vaccine must be stored at minus 70 degrees Celsius, equivalent to minus 94 degrees Fahrenheit. Pfizer created a special container to keep the shots cold during distribution.

The ultracold storage requirements have sent some health authorities and hospitals scrambling to find special freezers.

The U.S. has agreed to pay Pfizer and BioNTech nearly $2 billion for 100 million doses. Federal health officials said patients would be able to receive the shots free of charge.

The companies have struck similar supply agreements with other countries.

Write to Jared S. Hopkins at jared.hopkins@wsj.com

(END) Dow Jones Newswires

11-20-20 0659ET