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Moderna said Monday that its Covid-19 vaccine continued to deliver strong efficacy results, showing 94% efficacy in the main analysis of its key study. The company said it would immediately seek regulatory clearances in the U.S. and Europe.

The milestone suggests that there could be two vaccines against the SARS-CoV-2 virus before the end of 2020. Pfizer and BioNTech released positive results for a similar vaccine on Nov. 18, and requested an emergency use authorization, or EUA, from the Food and Drug Administration two days later.


“We believe that our vaccine will provide a new and powerful tool that may change the course of this pandemic and help prevent severe disease, hospitalizations and death,” said Stéphane Bancel, chief executive officer of Moderna, in a statement.

Moderna said it would make its request to the FDA on Monday, and would also apply for a conditional marketing authorization from the European Medicines Agency. Rolling applications with the EMA, Health Canada, Switzerland, the United Kingdom, Israel, and Singapore are ongoing, Moderna said.

In his statement, Bancel thanked people who volunteered for the vaccine studies, and Moderna’s partners at the National Institutes of Health, the U.S. Biomedical Advanced Research and Development Authority, and Operation Warp Speed, the U.S. government’s vaccine effort.


The two-dose vaccine was 94.1% effective based on a total of 196 cases of symptomatic Covid-19 occurring in the company’s 30,000-volunteer study. That means that 185 cases of Covid-19 occurred in those who received a placebo injection, which was given to half the volunteers. Just 11 cases occurred in those volunteers who received the vaccine.

The data “bolster” already strong results Moderna released previously, Natalie Dean, a statistician at the University of Florida, told STAT after reviewing Moderna’s press release. “With evidence of high efficacy against disease and severe disease, the vaccine checks a lot of boxes,” Dean said.

There were 30 cases of severe Covid-19 in the placebo group of the study, with none in the vaccine group. One volunteer in the placebo group died of Covid-19, compared to none in the vaccine group.

On Nov. 16, Moderna released a preliminary analysis of the 30,000-volunteer study, in which the vaccine was 94.5% effective at preventing Covid-19 based on 95 cases of symptomatic infection, 90 of them in the placebo group.

Moderna said that safety data is being reviewed continuously, but that there are no new serious safety concerns. The most common adverse events included site pain, fatigue, muscle or bone pain, headaches, and redness at the injection site. The reactions were more serious in the vaccine group after patients received a second dose. The results Pfizer and BioNTech released 12 days ago for their vaccine are roughly similar. That two-dose vaccine is 95% effective, the companies said in a press release. Of the 170 cases of Covid-19 observed in the Pfizer/BioNTech trial, 162 occurred in the placebo group and just eight among the group that received the vaccine. Of 10 cases of severe Covid-19, nine were in the placebo group.

It is not yet possible to say, however, how long the immunity granted by either vaccine will last, because studies of both have only lasted a matter of months.

The next step in the process relies on a panel of expert advisers to the FDA, called the Vaccines and Related Biological Products Advisory Committee, which will convene Dec. 10 to review Pfizer’s vaccine and recommend whether it should be cleared for use in health workers and other vulnerable populations. A committee meeting to review Moderna’s data is set to take place Dec. 17.

The FDA is expected to authorize both vaccines, which require two doses a few weeks apart. But the supply of each will be constrained well into next year. Pfizer has said it will be able to provide the U.S. government 25 million doses in December — enough to vaccinate 12.5 million people. Moderna expects to hand over 15 million doses this year, which would cover 7.5 million vaccinations.

The U.S. government has agreed to acquire 100 million doses of each vaccine with the option to purchase many more. It’s not clear, however, how quickly the companies can manufacture enough to vaccinate all 330 million Americans. Pfizer and BioNTech hope to manufacture up to 1.3 billion doses in 2021 to serve the entire world. Moderna said it is on track to produce 500 million to 1 billion doses of its vaccine globally in 2021.

Pfizer and Moderna both use messenger RNA, or mRNA, technology in their vaccines. Each strand of synthetic mRNA is designed to encode for a protein found on the surface of SARS-CoV-2, the virus that causes Covid-19. Those mRNA strands enter the body’s cells and instruct them to produce that protein. The immune system then recognizes it as a foreign invader and produces antibodies that protect against Covid-19 if a person is later exposed to the virus.

The Covid-19 vaccine would be Moderna’s first product approved by the FDA and, assuming Pfizer’s vaccine is approved first, only the second mRNA medicine ever licensed.

Moderna said that its vaccine’s efficacy was consistent regardless of age, race, or ethnicity. The 196 cases of Covid-19 included 33 in older adults, 29 in volunteers identifying as Hispanic or Latinx, six in Black volunteers, four among Asian American volunteers, and three in volunteers who identified as multiracial.

While the Pfizer/BioNTech and Moderna vaccines appear to be speeding toward regulatory clearance, other companies in the vaccine race appear to be hitting speed bumps. Last week, AstraZeneca released early results from its Covid-19 vaccine showing that the two-dose shot, which works differently from the Pfizer and Moderna vaccines, was 62% effective. But a version that used a lower first dose appeared 90% effective in a smaller group of patients, a result experts found puzzling. AstraZeneca’s CEO told Bloomberg last week that he expects it will need to conduct another study.

Novavax, which has two large studies of its Covid-19 vaccine ongoing in the U.K. and South Africa, said Monday that its Phase 3 study in the U.S. and Mexico, which had been expected to begin in November, would not. Instead, it said, the study will begin in the coming weeks.

  • Do we know whether the vaccine also blocks or reduces asymptomatic transmission? In other words, as more and more people get the vaccine, will we make progress toward herd immunity?

  • I’ve been quarantined 9 months 67 years old & alone. I can’t wait to try this miracle vaccine for Corona virus. Sign me up. I thank everyone who has made this new drug available for our country. So many loved ones gone from the virus hopefully this will stop all of loss & grief. God bless you all

  • How many volunteers in both groups had immune issues (cancers etc.) and what were the side effects on these volunteers? In addition, what percentage of volunteers in each group were over 65.

  • Severe side effects:
    Fatigue in 9.7% of participants, muscle pain in 8.9%, joint pain in 5.2%, and headache in 4.5% – Total 28.3% (assuming independent).
    Fatigue 3.8% and headache 2% – Total 5.8% (assuming independent).

    These are SEVERE side effects, not trivial fatigue, muscle/joint pain or headache.

    FDA should think really hard before approving Moderna or the confidence in vaccines will be lost. Money talks though… and NIH is hand in hand with FDA.

    • It’s been pretty well reported lately that the side effects have caused people to feel ill for a day or two. Those severe side effects I would think, outweigh the risk of catching COVID or transmitting your subclinical infection to your loved ones. I would hope public confidence in vaccines would be at an all-time high shortly after the population becoming vaccinated and watching COVID infections/hospitalizations/deaths plummet. These numbers on the data that has been publicly released so far looks very promising with minimal risks/side effects in the present data. If this data continues, this should be approved for use (read life saving) ASAP.

  • “The most common adverse events included site pain, fatigue, muscle or bone pain, headaches, and redness at the injection site. The reactions were more serious in the vaccine group after patients received a second dose.”

    And, what were the reactions after the second dose? How about some information on how severe they were, or does the company not want to share that? Also, the cohort is way too small to see the emergence of any less common reactions, and is there any information about those with comorbidities, especially autoimmune diseases? And the key question–how long does it last? The testing is 3 months. Well, the emergency authorization is simply a continuation of the phase 3 trial–so the public should be made well aware of that–whoever gets this vaccine now is really going to be part of the trial. You don’t unleash a vaccine, especially one made with a brand new technology, on the general public after a 3 month trial in a small population–and yes, 30,000 is small for a vaccine trial–and claim its perfectly safe and effective.

    • No one will know how long immunity is provided until each of those time frames are past. Is it a 10 year immunity? 5 year? 2 year? 6 month? Who knows it hasn’t been around for 10 years. It’s possible it does confur immunity for 10 years, we don’t know. Though we do know that there will be multiple unnecessary deaths from COVID infection.

      Also, the EUA is not a continuation of the phase 3 trial. And that is not a small population for a vaccine trial, it seems appropriate in relation to other vaccine trials.

      “The total number of subjects in Phase II trials for a vaccine ranged from 361 (IPOL) to 7,471 (Daptacel), with mean = 2,854 and median = 2,453. The number of subjects in Phase III trials for a vaccine ranged from 2,358 (IPOL) to 80,427 (Rotarix), with mean = 29,844 and median = 22,938. The total number of subjects in late phase (II + III) trials for a vaccine ranged from 2,719 (IPOL) to 86,801 (Rotarix), with mean = 32,698 and median = 26,985.”

  • @Rhona: That’s not how this works. You wait until you have a certain number of “natural” infections and then check how many of those got the placebo and how many got the actual vaccine.

    Human challenge trials are only theoretically helpful. You couldn’t ethically really expose a 70-year old.

  • One would expect that the volunteers in the clinical trial would be vaccinated and then exposed to Covid-19 to see if the vaccine prevents disease. Is this done? Were the 196 cases of Covid due to random infection or were all volunteers equally exposed?

    • “Were the 196 cases of Covid due to random infection or were all volunteers equally exposed”.

      That’s why it is a double blind randomised placebo controlled trial. So any variations in exposure due to location, propensity to engage in high risk activity etc are equally occurring in each of the placebo and the active arm.

      Realistically though your point strongly suggests the vaccine is even MORE effective than 94.1%. Reason being that those given the saline placebo would be more likely to correctly assume they are NOT protected given a complete lack of side effects (aide effects have been pretty well publicised for weeks). Thus they would have taken more protections than those who assumed they were protected after experiencing side effects of the vaccine.

      This vaccine needs to be approved PRONTO.

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