The announcement came after the results of an earlier trial to prove that the vaccine was safe and that the production of triggered antibodies had been published.
The next phase 3 trial will recruit 30,000 participants in the United States, half of whom will receive the vaccine at 100 microgram doses and the other half of whom will receive a placebo.
The researchers will then follow them over two years to determine if they are protected against infection by the virus. Or, if they become infected, if the vaccine prevents symptoms from developing.
If they experience symptoms, the vaccine can still be considered successful if it stops severe cases of Covid-19.
The study is expected to continue until October 27, 2022, but preliminary results should be available well in advance.
The announcement came shortly after the New England Journal of Medicine published the results of the first stage of the Moderna vaccine trial, which showed that the first 45 participants had all developed antibodies to the virus.
Moderna is considered a leading position in the global race to find a vaccine against the coronavirus, which has infected more than 13.2 million people and killed 570,000 people.
But scientists warn that the first vaccines on the market may not be the most effective or the safest.
Moderna previously released “interim results” of the early stages of its trial, called Phase 1 in May.
The first results were deemed “encouraging” by Anthony Fauci, director of the US National Institute of Allergies and Infectious Diseases, which is co-developing the vaccine.
But some members of the scientific community have said they will reserve judgment until they see the full results in a peer-reviewed form.
According to the document, 45 participants were divided into three groups to test doses of 25 micrograms, 100 micrograms and 250 micrograms.
They received a second dose of the same amount 28 days later.
After the first cycle, antibody levels were found to be higher with higher doses.
After the second round, participants had higher antibody levels than most patients who had Covid-19 and continued to generate their own antibodies.
More than half of the participants experienced mild or moderate side effects, which is considered normal.
Side effects included fatigue, chills, headache, body aches, and pain at the injection site.
Three participants did not receive their second dose.
They included one who developed a rash on both legs and two who missed their window because they had symptoms of Covid-19, but their tests then returned negative.
Amesh Adalja, an infectious disease specialist at Johns Hopkins University, said it was encouraging that participants had developed high levels of an advanced class of antibodies.
He added, however, “You have to be very limited in the amount of extrapolations from a phase one clinical trial because you want to see how it works when a person is exposed to the actual virus. ”
The Moderna vaccine belongs to a new class of vaccines which uses genetic material – in the form of RNA – to encode the information necessary for the growth of the virus’s advanced protein in the human body, in order to trigger an immune response.
Peak protein is part of the virus it uses to invade human cells, but the protein itself is relatively harmless.
The advantage of this technology is that it bypasses the need to make viral proteins in the laboratory, thereby helping to speed up mass production.
No vaccine based on this platform has previously received regulatory approval.
Early work using this technology backfired, making hosts more, not less, susceptible to infection, said David Lo, professor of biomedical science at the University of California Riverside.
“One of the things we certainly want to look for is whether there is a long-term effect where the immune response … potentially develops an immunological tolerance which would actually be detrimental to protection,” he said.