Early Data Show Moderna’s Coronavirus Vaccine Is 94.5% Effective

[Read more on Moderna’s Covid-19 vaccine.]

The drugmaker Moderna announced on Monday that its coronavirus vaccine was 94.5 percent effective, joining Pfizer as a front-runner in the global race to contain a raging pandemic that has killed 1.2 million people worldwide.

Both companies plan to apply within weeks to the Food and Drug Administration for emergency authorization to begin vaccinating the public. Officials said the two companies could produce enough vaccine for a little more than 20 million people in the United States by sometime in December, with the first doses going to people with the highest risk, like health care workers, emergency medical workers and frail residents of nursing homes.

But a vaccine that would be widely available to the public is still months away, while the need for one is becoming increasingly urgent.

The pandemic has infected more than 53 million people around the world so far. U.S. cases are soaring, setting records every day. There have been more than 11 million cases and 246,000 deaths. Covid-19 is killing more than 1,100 Americans a day, and the last million cases occurred in just six days.

Some states and cities are reinstating lockdowns, restricting gatherings, issuing mask mandates, setting curfews for bars and restaurants, and closing schools once again. Hospitals in some areas are overwhelmed, scrambling to find enough beds for the severely ill. Major grocery chains like Kroger and Wegmans have begun reimposing limits on purchases of household supplies like paper towels and tissues.

Despite those sobering measures, the stock market rallied on Monday, fueled by Moderna’s news. But businesses and others braced for what could be a bleak holiday season with Covid’s grip on the nation’s citizens and its economy.

Public health officials greeted Moderna’s news with a modicum of excitement, especially when viewed alongside the data released last week by Pfizer, which, in collaboration with BioNTech, reported that its vaccine was more than 90 percent effective. The two companies were the first to announce interim data from large studies. Ten other vaccine makers are also conducting big Phase 3 trials, including efforts in Australia, Britain, China, India and Russia. More than 50 other candidates are in earlier stages of testing.

The Pfizer and Moderna vaccines far exceeded the Food and Drug Administration’s requirement that coronavirus vaccines be at least 50 percent effective to receive approval.

Moderna also reported on Monday that its vaccine had a longer shelf life under refrigeration and at room temperature than previously reported, which should make it easier to store and use.

Based in Cambridge, Mass., the company developed its vaccine in collaboration with researchers from the Vaccine Research Center, part of the National Institute of Allergy and Infectious Diseases.

Dr. Anthony S. Fauci, director of the institute, said in an interview: “I had been saying I would be satisfied with a 75 percent effective vaccine. Aspirationally, you would like to see 90, 95 percent, but I wasn’t expecting it. I thought we’d be good, but 94.5 percent is very impressive.”

Researchers test vaccines by inoculating some study participants and giving others placebos, and then watching the two groups to see how many people get sick. In Moderna’s study, 95 people contracted the coronavirus: five who were vaccinated, and 90 who received placebo shots of saltwater. Statistically, the difference between the two groups was highly significant. And of the 95 cases, 11 were severe — all in the placebo group.

The 95 cases included 15 people 65 or older and 20 people who were Hispanic, Black, Asian or multiracial. The company said the vaccine appeared equally safe and effective in all the subgroups.

The results were analyzed by an independent data safety monitoring board, appointed by the National Institutes of Health.

At a news briefing on Monday, Dr. Fauci and Dr. Francis Collins, director of the National Institutes of Health, emphasized that the hopeful news did not mean people could let down their guard. On the contrary, they implored the public to “double down” on mask-wearing, social distancing, hand-washing and avoiding crowds, and to stay that course until vaccines become available.

That message was echoed by the head of the World Health Organization, Dr. Tedros Adhanom Ghebreyesus, who said in a video, “A vaccine on its own will not end the pandemic.”

Stéphane Bancel, the chief executive of Moderna, said in a statement that the results had provided “the first clinical validation that our vaccine can prevent Covid-19 disease, including severe disease.”

Pfizer’s chief executive, Dr. Albert Boula, tweeted congratulations to Moderna.

But the companies announced the findings in news releases, not in peer-reviewed scientific journals, and did not disclose the detailed data that would allow outside experts to evaluate their claims. Therefore, the results cannot be considered conclusive. The figures on effectiveness may change as the studies continue.

The companies’ products open the door to an entirely new way of creating vaccines — and creating them fast. Both use a synthetic version of coronavirus genetic material, called messenger RNA or mRNA, to program a person’s cells to churn out many copies of a fragment of the virus. That fragment sets off alarms in the immune system and stimulates it to attack, should the real virus try to invade. Although a number of vaccines using this technology are in development for other infections and cancers, none have yet been approved or marketed.

“The fact that two different vaccines made by two different companies with two different kinds of structures, in a new messenger RNA concept, both worked so effectively confirms the concept once and for all that this is a viable strategy not only for Covid but for future infectious disease threats,” said Dr. Barry R. Bloom, a professor of public health at Harvard.

Natalie E. Dean, a biostatistician at the University of Florida, said an important finding was that the vaccine appeared to prevent severe forms of the disease. Pfizer did not release information about disease severity when reporting its results.

Researchers say the positive results from Pfizer and Moderna bode well for other vaccines, because all of the candidates being tested aim at the same target — the so-called spike protein on the coronavirus that it uses to invade human cells.

Dr. Bloom said that the success of the two vaccines meant that measures of immunity used in earlier phases of the studies — participants’ antibody levels — were reliable, and that other companies could use those measures as proof of effectiveness to shorten the testing and approval process for their vaccines.

It will be important to determine whether the vaccines work equally well in older and younger people, experts say. Researchers also want to know if the vaccines prevent people from spreading the virus — an ideal result that could help quash the pandemic.

Another big unknown is how long the immunity provided by the vaccines will last.

An additional concern is that both vaccines must be stored and transported at low temperatures — minus 4 degrees Fahrenheit for Moderna, and minus 94 Fahrenheit for Pfizer — which could complicate their distribution, particularly to low-income areas in hot climates. Although both vaccines are made of mRNA, their temperature requirements differ because they use different, proprietary formulations of fat to encase and protect the mRNA, Ray Jordan, a Moderna spokesman, said.

Other coronavirus vaccines being developed will need only refrigeration. If handled improperly, vaccines can become inactive.

But on Monday, Moderna said researchers had found that its vaccine had a longer shelf life in the refrigerator than previously thought: 30 days, not seven. And it will last 12 hours at room temperature, the company said.

Dr. William Schaffner, an infectious disease expert at Vanderbilt University, said the relative ease of handling the Moderna vaccine would give it a big advantage.

“This vaccine presents the opportunity of using doctors’ offices, clinics and pharmacies as vaccination sites,” he said, adding that he would not be surprised, should both vaccines become available, if vaccination sites requested Moderna’s.

Coronavirus Vaccine Tracker

A look at all the vaccines that have reached trials in humans.

So far, studies of the two vaccines have not found serious side effects, but participants have reported sore arms, fatigue, fever, and joint and muscle aches that last for a day or two.

Moderna’s study did not include children. Dr. Tal Zaks, the company’s chief medical officer, said the company planned to test it in them in the coming months, starting with adolescents.

Moderna said it would have 20 million doses ready by the end of 2020; Pfizer said it would have about 50 million by then — half for Americans. Both vaccines require two shots, so 20 million doses would be enough for 10 million people.

On Friday, Moncef Slaoui, the chief scientist for Operation Warp Speed, the Trump administration’s program to accelerate development of vaccines and treatments for Covid-19, said that if any early vaccine candidates received permission for emergency use, immunization could begin sometime in December.

The U.S. government will buy the vaccines and give them to the public for free. But both companies expect to profit, and not to provide their products at cost. Moderna said it would charge other governments from $32 to $37 per dose. The charge to the United States, which has already committed about $2.5 billion to help develop Moderna’s vaccine and buy doses, comes out to about $24.80 a shot, according to Mr. Jordan, the company spokesman.

Pfizer did not take any money from the U.S. government to develop or test its vaccine. But Operation Warp Speed has promised Pfizer $1.95 billion to provide 100 million doses, which comes out to $19.50 per dose.

Both of the companies’ vaccine candidates began large human trials on the same date, July 27.

Moderna had planned a first interim analysis of its trial data when the number of Covid-19 cases among participants reached 53. But the accelerating surge in coronavirus cases drove the number to 95, and it is likely to speed completion of the study, which was designed to stop after 151 cases.

The company announced on Oct. 22 that it had completed enrollment of its 30,000-person study, and that 25,650 participants had already received two shots. The company had slowed enrollment in September to ensure diversity among participants, and ultimately included 37 percent from communities of color, and 42 percent from populations considered at high risk because they were over 65 or had conditions like diabetes, obesity or heart disease.

As in Pfizer’s study, half of the participants were given the experimental vaccine and half a placebo shot of saltwater, with neither the patients nor their doctors knowing which one they had received. Moderna’s vaccine requires four weeks between shots, and Pfizer’s needs three weeks.

Dr. Zaks said Moderna’s study results were so strong that the company felt an ethical obligation to offer the vaccine to the placebo group as soon as possible, if the F.D.A. allows it.

Moderna said it could produce 500 million to one billion doses in 2021.

The company is working with the Swiss company Lonza and Laboratorios Farmacéuticos Rovi of Spain to make doses of the vaccine outside the United States.

Dr. Bloom, the Harvard professor, noted that Moderna had never marketed a vaccine before, and he questioned whether the company had the capacity to manufacture hundreds of millions of doses.

Moderna has received a commitment of $955 million from the U.S. government’s Biomedical Advanced Research and Development Authority for research and development of its vaccine, and the United States has committed up to $1.525 billion to buy 100 million doses.

Moderna has already taken the early steps needed to apply to government agencies in Britain, Canada and Europe to market its vaccine, and the company has made deals to sell 50 million doses to Japan and unspecified amounts to Qatar and Israel.

Shares of Moderna rose nearly 10 percent on Monday, to almost $98 a piece by the market’s close.

Carl Zimmer and Michael de la Merced contributed reporting.

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