More than 100 vaccines are being studied for COVID-19 infection, and at least eight of these, including Moderna's, have already progressed to human studies.
Importantly, the vaccine appears to be "generally safe and well-tolerated" with no life-threatening side effects, the company said.
The early readout included arms of the trial involving people ages 18 to 55 years old who received either two doses at the 25 microgram or 100 microgram level or one dose at 250 microgram.
The National Institutes of Health is leading this initial trial, and taxpayers have invested a half-billion dollars in the later-stage trials. CEO Stéphane Bancel said the company is pushing forward with a Phase 3 trial set to start in July and is ramping up its capacity to manufacture the vaccine.
The company said that grant will enable it to supply millions of doses per month in 2020 and, with further investments, tens of million a month in 2021 if the vaccine proves successful. People who received two doses at 100 microgram had binding antibody levels that "significantly exceeded" the levels seen in the blood of Covid-19 survivors. The study was split so that 15 participants took a low dose, 15 took a mid-level dose, and 15 took a high dose.
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Army Material Command, was appointed to lead the effort on the Department of Defense side. That's faster than any new vaccine ever has reached this point in development.
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Silver said the individual would be removed from the playing or practice environment and those around him would undergo more testing.
Samples are not yet available for the remaining participants, Moderna said.
The company said it hopes to proceed to a Phase 3 trial in July.
A vaccine or treatment that gets the status is eligible for more frequent meetings with the FDA.
President Trump may have referred to the Moderna trial when he spoke briefly to reporters Sunday at the White House upon returning from Camp David.
Those people, healthy volunteers, made antibodies that were then tested in human cells in the lab and were able to stop the virus from replicating - the key requirement for an effective vaccine.
Follow-up data was more limited for the higher doses, as the volunteers are still being tracked. Dr. Anthony Fauci said during a Senate hearing last Tuesday that the NIH would know by fall or early winter if the NIH vaccine would be effective, and on Friday, President Donald Trump said it was his plan to have a vaccine widely available by January 1. At a medium dose, of 100 micrograms, he said, the vaccine candidate created "more antibodies" than those created naturally by recovered patients. How many doses might be ready is not clear, but Zaks said, "We're doing our best to make it as many millions as possible".
China has said that it is carrying out tests on humans of five experimental vaccines. Moderna said the vaccine "prevented viral replication in the lungs" of these mice.