The U.S. arsenal against COVID-19 strengthened Wednesday as federal regulators said Johnson & Johnson’s vaccine against the coronavirus was safe and effective.

The company tested its single-dose vaccine on more than 40,000 people globally and found mixed results against the various strains of the coronavirus that causes COVID-19.

In general, the Food and Drug Administration found the vaccine was 66% effective, far less than that of the approved Pfizer/BioNTech and Moderna two-dose options.

The FDA is evaluating whether that’s effective enough for approval, a matter up for debate at a formal hearing on Friday. A final decision on the single-dose vaccine could follow in a matter of days, The Associated Press reported Wednesday.

The White House is getting ahead of the word on final emergency-use approval, announcing Johnson & Johnson will have 3 to 4 million doses available next week, CNN reported.

Meanwhile, a report by ABC News said the company’s studies found the vaccine is indeed effective against all variants, but less so for the South African strain. Despite the lower rate of effectiveness against catching the virus, the Johnson & Johnson vaccine is nearly 100% effective against serious illness and death.

On Friday, Johnson & Johnson filed for emergency-use authorization of its vaccine with the World Health Organization. The process helps advance widespread use and supplies vaccines to the so-called COVAX facility, a global entity meant to facilitate worldwide distribution, including to 92 economically challenged countries.

“If we are to end the global pandemic, lifesaving innovations like vaccines must be within reach for all countries,” Paul Stoffels, the chief science officer said in a statement.

Though less effective than the two drugs already in use in the U.S., the Johnson & Johnson dose can be stored for up to three months in a refrigerator without spoiling. Both Pfizer’s and Moderna’s require sub-zero storage temperatures and only last a few hours once the vials are opened.

The breakthrough for the expected approval of another vaccine comes as lawmakers express doubt about the pace of the U.S. inoculation effort. Lawmakers said earlier this week they expected Pfizer and Moderna to fall short of a goal of producing 220 million doses by April.

“Many of these companies received significant federal investment to build their manufacturing capacity last year so that we would be able to rapidly deliver millions of vaccines as soon as they were authorized,” Rep. Diana DeGette, D-Colo., chair of the House Energy and Commerce oversight subcommittee, said this week. “Two vaccines have been authorized and production is ramping up, but there is still insufficient supply to meet current demand.”

Representatives from Johnson & Johnson told Congress they expect to have 20 million doses available by March and 100 million by the middle of the year.

President Joe Biden earlier this week ordered national flags at half-staff to commemorate the lives of the more than 500,000 people nation-wide who died as a result of complications from COVID-19.

In this file photo taken on August 28, 2019 an entry sign to the Johnson & Johnson campus shows their logo in Irvine, California
In this file photo taken on August 28, 2019 an entry sign to the Johnson & Johnson campus shows their logo in Irvine, California AFP / Mark RALSTON