This is the biggest COVID-19 study of its kind so far.
In a press release, the company said analysis of trial results for its potential COVID-19 vaccine "mRNA-1273" reaffirmed the "positive interim data assessment" it announced mid-May when the drug first showed a "potential to prevent" the deadly and infectious coronavirus.
BofA analysts note the data leaves them with "more questions unanswered" even though they assign a higher probability of success to the vaccine (45% from 25%) and boost their price target on the expectation that shares would trade up on the news.
Vanderbilt University Medical Center says it will begin recruiting 1,000 volunteers in late July for a late-stage study of an experimental COVID-19 vaccine. Moderna started its phase 2 trial in May and expects to start a phase 3 trial on July 27.
But some in the scientific community said they would reserve judgment until they saw the full results in peer-reviewed form.
The interim report details the initial findings from the first 45 participants aged 18 to 55 years enrolled in the Phase I dose-escalation study at sites in Seattle and at Emory University in Atlanta, both US.
They were given a second dose of the same amount 28 days later.
The researchers reported that the two doses of the vaccine did prompt high levels of antibody activity.
More than half the participants experienced mild or moderate side effects, which is considered normal. More than 50% of the participants reported fatigue, headache, chills, myalgia, or pain at the injection site; however, there were no serious adverse events.
"Seroconversion was rapid for binding antibodies, occurring within 2 weeks after the first vaccination, but pseudovirus neutralizing activity was low before the second vaccination, which supports the need for a two-dose vaccination schedule", investigators wrote. Moderna itself is turning out vaccine supplies for the US market at its site in MA and in conjunction with partner Lonza, which is producing supplies in New Hampshire, Bancel said.
The company aims to enroll 30,000 adults in the clinical trial, which is created to test whether the vaccine works to prevent COVID-19. The spike protein is a part of the virus that it uses to invade human cells, but by itself the protein is relatively harmless.
Although a vaccine that triggers antibody production does not prove its efficacy, it is still an important step in testing.
No vaccines based on this platform have previously received regulatory approval.