• mRNA-1273 was tested on healthy subjects between the ages of 18 and 55
  • By the 43rd day of the test, after two doses, subjects were producing more antibodies than people who had recovered from the disease
  • The company hopes to begin phase 3 trials by July

Moderna said Monday it had obtained initial positive results from its trial of a vaccine for the coronavirus. The trial of mRNA-1273 began in March.

mRNA stands for messenger RNA.

Phase 2 trials are expected to begin within days. Researchers said the vaccine showed evidence it could prevent the virus from replicating in the body.

The biotechnology company said test subjects received two doses of the vaccine as part of a phase 1 study led by the National Institute of Allergy and Infectious Diseases.

“These interim Phase 1 data, while early, demonstrate that vaccination with mRNA-1273 elicits an immune response of the magnitude caused by natural infection starting with a dose as low as 25 µg [microgram],” Dr. Tal Zaks, Moderna’s chief medical officer, said in a press release.

“When combined with the success in preventing viral replication in the lungs of a pre-clinical challenge model at a dose that elicited similar levels of neutralizing antibodies, these data substantiate our belief that mRNA-1273 has the potential to prevent COVID-19 disease and advance our ability to select a dose for pivotal trials.”

The press release did not specify the number of subjects in the trial. Phase 2 trials for the last 13 vaccines approved typically involved 361 to 7,471 subjects, and phase 3 trials can involved tens of thousands.

As of midmorning Monday, COVID-19 had killed nearly 90,000 Americans.

The company tested three levels of dosage on trial healthy subjects between the ages of 18 and 55. All subjects began producing antibodies to the virus by the 15th day after they received the first dose. By the 43rd day, two weeks after receiving a second dose, researchers said they began seeing antibodies at a higher level than what was typically seen in the blood serum of patients who had recovered by COVID-19.

The only adverse reaction occurred in one test subject who developed redness around the injection site.

“With today’s positive interim Phase 1 data and the positive data in the mouse challenge model, the Moderna team continues to focus on moving as fast as safely possible to start our pivotal Phase 3 study in July and, if successful, file a BLA [biologics license application from the Food and Drug Administration],” CEO Stéphane Bancel said. “We are investing to scale up manufacturing so we can maximize the number of doses we can produce to help protect as many people as we can.”

President Trump said last week he expected a vaccine to be available by the end of the year and pledged to gear up production before final FDA approvals are given. He also said the military would be used to distribute the vaccine rapidly.