Moderna said Monday its COVID-19 vaccine is proving to be highly effective in a major trial, another dash of hope in the global race to tame the coronavirus.

The company revealed its vaccine appears to be 94.5% effective, according to preliminary data. Last week, Pfizer announced its own vaccine is similarly effective.

A vaccine can’t come fast enough, as virus cases topped 11 million in the U.S. over the weekend — 1 million of them recorded in just the past week — and governors and mayors are ratcheting up restrictions ahead of Thanksgiving. The pandemic has killed more than 1.3 million people worldwide, over 245,000 of them in the U.S.

If the FDA allows emergency use of Moderna’s or Pfizer’s candidate, there will be limited, rationed supplies before the end of the year.

When will a COVID-19 vaccine be available in the United States?

Both vaccines require people to get two shots, several weeks apart. U.S. officials said they hope to have about 20 million Moderna doses and another 20 million doses of the vaccine made by Pfizer and its German partner BioNTech to use in late December.

According to the CDC, when a vaccine is authorized or approved in the United States, there may not be enough doses available for all adults. “Supplies will increase over time, and all adults should be able to get vaccinated later in 2021,” the CDC wrote on the official Operation Warp Speed website. “However, a COVID-19 vaccine may not be available for young children until more studies are completed.”

On Sunday,  Moderna CEO Stéphane Bancel told Business Insider a vaccine will be available to anyone who wants it by the end of May 2021.

“What I believe is that by Memorial Day, in the US, anybody who wants a vaccine will get a safe and efficacious vaccine,” Bancel said on Sunday.

Bancel made the estimate based on production estimates at Moderna and Pfizer.

Once submitted, experts say it should take 10 days for the FDA to review Pfizer’s clinical trial data. This data is not yet available. The data released by Pfizer last week was only “preliminary.”

Pfizer is not expected to receive authorization from the U.S. Food and Drug Administration before the last two weeks of December.

Who will receive a vaccine?

Exactly who is first in line is yet to be decided. But Health and Human Services Secretary Alex Azar said the hope is that enough doses are available by the end of January to vaccinate adults over 65, who are at the highest risk from the coronavirus, and health care workers.

Dr. Anthony Fauci, the U.S. government’s top infectious diseases expert, said it may take until spring or summer for enough for anyone who is not high risk and wants a shot to get one.

On Sunday, Fauci speculated the United States could get “back to normal” over the summer next year.

Here’s what we know about the Moderna trial

Moderna’s vaccine is being studied in 30,000 volunteers who received either the real thing or a dummy shot. On Sunday, an independent monitoring board examined 95 infections that were recorded after volunteers’ second dose, and they discovered all but five illnesses occurred in participants who got the placebo.

The study is continuing, and Moderna acknowledged the protection rate might change as more COVID-19 infections are detected. Also, it’s too soon to know how long protection lasts. Both cautions apply to Pfizer’s vaccine as well.

But Moderna’s independent monitors reported some additional, promising tidbits: All 11 severe COVID-19 cases were among placebo recipients, and there were no significant safety concerns. The main side effects were fatigue, muscle aches and injection-site pain after the second dose.

The Cambridge, Massachusetts, company’s vaccine is among 11 candidates in late-stage testing around the world, four of them in huge studies in the U.S.

More vaccines being tested

Additional vaccines that work in different ways are still in testing — and despite the promising news about Moderna’s and Pfizer’s shots, more volunteers are needed for those studies.

Both Moderna’s shots and the Pfizer-BioNTech candidate are so-called mRNA vaccines, a brand-new technology. They aren’t made with the coronavirus itself, meaning there’s no chance anyone could catch it from the shots. Instead, the vaccine contains a piece of genetic code that trains the immune system to recognize the spiked protein on the surface of the virus.

Johnson and Johnson announced on Monday a new large-scale late-stage trial to test its COVID-19 vaccine. The company said it expects to enroll 30,000 participants for a trial that will run in parallel with its one-dose trial that started in September.

Chilly vaccine challenges

Both the Moderna and Pfizer shots are frozen but at different temperatures. Moderna said that once thawed, its doses can last longer in a refrigerator than initially thought, up to 30 days. Pfizer’s shots require long-term storage at ultra-cold temperatures.

Pfizer CEO Albert Bourla tweeted that that he was thrilled at Moderna’s news, saying, “Our companies share a common goal — defeating this dreaded disease.”

The Associated Press contributed to this report.