Moderna Vaccine Is Highly Protective and Prevents Severe Covid-19, Data Show

WASHINGTON — The coronavirus vaccine made by Moderna is highly protective for adults and prevents severe cases of Covid-19, according to data released on Tuesday by the U.S. Food and Drug Administration.

Based on the encouraging findings, the agency intends to grant emergency authorization for use of the vaccine on Friday, people familiar with the F.D.A.’s plans said. The decision would give millions of Americans access to a second coronavirus vaccine beginning as early as next week.

The review by the F.D.A. confirms Moderna’s earlier assessment that its vaccine had an efficacy rate of 94.1 percent in a trial of 30,000 people. Side effects, including fever, headache and fatigue, were unpleasant but not dangerous, the agency found.

The success of Moderna’s vaccine has become all the more crucial to fighting the pandemic as other vaccine efforts have faltered. The hopeful news arrives at a time of record-breaking numbers of coronavirus cases that are overwhelming hospitals and of an ever-increasing death toll, which reached a bleak milestone of 300,000 on Monday.

The data release is the first step of a public review process that will include a daylong meeting on Thursday by an independent advisory panel of experts. They will hear from Moderna, F.D.A. scientists and the public before voting on whether to recommend authorization. The panel is expected to vote yes, and the F.D.A. generally follows the experts’ recommendations.

Distribution of about six million doses could then begin next week, significantly adding to the millions of doses already being shipped by Pfizer and BioNTech, the companies that developed the first coronavirus vaccine given emergency clearance just last Friday. Health care workers received the first shots on Monday of the Pfizer-BioNTech vaccine, which has an efficacy rate of 95 percent.

The vaccine rollout has been highly anticipated, and is one of the most ambitious immunization campaigns ever conducted in the United States.

The federal government signed deals last summer with Moderna and Pfizer to deliver a total of 200 million doses in the first quarter of 2021. Because both vaccines require two doses, those contracts guaranteed enough doses for 100 million people.

Last week the government announced that it had purchased another 100 million doses from Moderna for the second quarter, increasing the number of Americans who can be vaccinated to 150 million. But that still leaves the question of how and when the roughly 180 million other Americans will be covered.

Both vaccines will be provided to the public free of charge.

How Moderna’s Vaccine Works

Two shots can prime the immune system to fight the coronavirus.

Moderna’s vaccine has become a symbol of the triumphs of government scientists during the pandemic. After China released the genetic sequence of the new virus in early January, scientists at Moderna and the National Institutes of Health were able to zero in on the design for a vaccine in just two days. Unlike Pfizer, Moderna has maintained a close relationship with Operation Warp Speed, the federal program intended to quickly bring a vaccine to market. Nearly $2.5 billion in federal funds helped Moderna buy raw materials, expand its factory and enlarge its work force by 50 percent.

Moderna’s success stands in contrast to two other high-profile projects that the United States had hoped would augment its supply of vaccines: one from the pharmaceutical companies Sanofi of France and GlaxoSmithKline of Britain, and another from the British-Swedish drug maker AstraZeneca and the University of Oxford.

AstraZeneca and Oxford ended up using two different doses in clinical trials in Britain and Brazil. At one level, the efficacy was 62 percent, and at the other it was 90 percent. These muddled results have left it unclear when AstraZeneca will have enough data to secure an emergency use authorization.

Meanwhile, Sanofi and GlaxoSmithKline received disappointing results from their vaccine in early clinical trials. While it produced a promising immune response in volunteers under 50, it failed to do so in older ones. The companies are now planning a new set of trials with a different version of the vaccine. The delay means they would be unlikely to provide vaccines before the end of 2021.

Moderna’s vaccine worked equally well in white volunteers and in communities of color. There was also no significant difference between its protection for men and women, or between healthy volunteers and those at risk of severe Covid-19 who had conditions like obesity and diabetes. For people 65 and older, the trial provided an estimated efficacy of 86.4 percent, lower than the overall estimate of 94.1 percent. But the apparent difference was not statistically significant.

So far, two potential differences between the vaccines have emerged from the F.D.A.’s reviews, but the findings may reflect a shortage of data rather than genuine differences. The Pfizer-BioNTech trial showed that their vaccine started to protect against the coronavirus within about 10 days of the first dose. The trial of Moderna’s vaccine, by contrast, did not reveal such a striking effect after the first dose.

But fewer cases of Covid-19 occurred among trial participants in the early days of the Moderna trial, making it harder to measure differences between the vaccinated group and the placebo group. In any case, health officials have said that for both vaccines, two doses are essential for full protection.

A second difference involves the ability to prevent severe disease. Moderna produced more evidence that its vaccine can do so, according to the review. In its trial, 30 volunteers developed severe cases of Covid. All of them were in the placebo group, with no cases among the people who were vaccinated.

In the Pfizer-BioNTech trial, the findings were less compelling. There were 10 severe cases in the placebo group and one in the vaccinated group. Those numbers are too small to gauge the vaccine’s ability to prevent serious illness.

“The available data for these outcomes did not allow for firm conclusions,” the F.D.A. said.

The documents published Tuesday made clear that side effects were particularly common after the second dose, but typically lasted only a day. Experts say people may need to take a day off work after getting the shot.

During the Moderna trial, researchers also kept an eye out for volunteers who developed new disorders. In a trial lasting several months with 30,000 volunteers, it is normal for some to come down with conditions that have nothing to do with the vaccine, health experts say. Comparing the rates between the people who get the vaccine and the placebo — as well as general background rates — can help pinpoint serious concerns and rule out coincidences.

Emerging Treatments for Covid-19

Words to Know About Covid-19 Treatment

Confused by the terms used about how to treat Covid-19? Let us help:

    • ACE-2: A protein that sits on the surface of certain types of human cells. The coronavirus has to bind to ACE-2 in order to enter cells.
    • Adverse event: A health problem that crops up in volunteers in a clinical trial of a vaccine or a drug. An adverse event isn’t always caused by the treatment tested in the trial.
    • Antibody: A protein produced by the immune system that can attach to a pathogen such as the coronavirus and stop it from infecting cells.
    • Antiviral drug: A drug that interferes with a virus’s ability to replicate inside cells. The first approved drug for Covid-19 in the United States, remdesivir, is an antiviral.
    • Approval, licensure and emergency use authorization: Drugs, vaccines and medical devices cannot be sold in the United States without gaining approval from the Food and Drug Administration, also known as licensure. After a company submits the results of clinical trials to the F.D.A. for consideration, the agency decides whether the product is safe and effective, a process that generally takes many months. If the country is facing an emergency — like a pandemic — a company may apply instead for an emergency use authorization, which can be granted considerably faster.
    • Compassionate use: A term used to describe treatments that are given to seriously ill people despite not yet being approved by the Food and Drug Administration for that use.
    • Cytokine storm: A hyperactive response from the immune system that can lead to massive amounts of inflammation and tissue damage. Cytokine storms may be responsible for many of the severe cases of Covid-19, and a number of researchers are testing drugs that might be able to quiet them.
    • Interferon: A molecule made by the immune system. Certain types of interferons can unleash inflammation in the body, while others tamp it down. Yet other types can spur cells to strengthen their defenses against viruses. Researchers are exploring whether treatments of synthetic interferons can help people fight off the coronavirus.
    • Monoclonal antibodies: Monoclonal antibodies, created in a laboratory, mimic the natural antibodies produced by the immune system. A number of companies have developed these treatments for Covid-19. President Trump received Regeneron’s antibody treatment shortly after he was diagnosed with the disease.
    • Phase 1, 2, and 3 trials: Clinical trials typically take place in three stages. Phase 1 trials usually involve a few dozen people and are designed to observe whether a vaccine or drug is safe. Phase 2 trials, involving hundreds of people, allow researchers to try out different doses and gather more measurements about the vaccine’s effects on the immune system. Phase 3 trials, involving thousands or tens of thousands of volunteers, determine the safety and efficacy of the vaccine or drug by waiting to see how many people are protected from the disease it’s designed to fight.
    • Placebo: A substance that has no therapeutic effect, often used in a clinical trial. To see if a vaccine can prevent Covid-19, for example, researchers may inject the vaccine into half of their volunteers, while the other half get a placebo of salt water. They can then compare how many people in each group get infected.
    • Post-market surveillance: The monitoring that takes place after a vaccine or drug has been approved and is regularly prescribed by doctors. This typically confirms that the treatment is safe. On rare occasions, it detects side effects in certain groups of people that were missed during clinical trials.
    • Preclinical research: Studies that take place before the start of a clinical trial, typically involving experiments where a treatment is tested on cells or in animals.
    • Trial protocol: A series of procedures to be carried out during a clinical trial.
    • Retrospective study: A study that analyzes data collected in the past to assess how effective a treatment is. Retrospective studies can offer useful insights, but are not as definitive as randomized clinical trials.
    • Spike protein: A protein that sits on the surface of coronaviruses. The spike protein binds to the ACE-2 receptor on human cells using a region called the receptor-binding domain (R.B.D.). Once the protein attaches, the virus can enter the cell. Many vaccines and monoclonal antibody treatments are designed to attach to the spike.
    • Standard of care: A treatment accepted by medical experts as a proper way to treat a certain type of disease. Once a standard of care emerges for a disease, any new experimental treatments are typically tested against it, rather than against a placebo.

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