First Coronavirus vaccine tested in humans shows early promise

Moderna's vaccine offered a promising immune response against Covid-19 in the first 45 people who received it; next phase will involve testing on 30,000 people, beginning July 27

By Denise Grady

Published: Jul 15, 2020

Image: Shutterstock

An experimental coronavirus vaccine made by the biotech company Moderna provoked a promising immune response against the virus and appeared safe in the first 45 people who received it, researchers reported Tuesday in The New England Journal of Medicine.

Moderna’s vaccine, developed by researchers at the National Institute of Allergy and Infectious Diseases, was the first coronavirus vaccine to be tested in humans, and the company announced on Tuesday that large Phase 3 tests of it would begin on July 27, involving 30,000 people. Half of the participants will be a control group who will receive placebos.

This large clinical trial is expected to be completed by late October. But it’s not clear whether it will be possible to prove the vaccine is safe and effective by then. The trial will need to show that those who were vaccinated were significantly less likely to contract the virus than those who got a placebo. The fastest way to get results is to test the vaccine in a “hot spot” with many cases, and the study is looking for people at high risk because of their locations or circumstances.

Vaccines and improved treatments are the only hope of returning lives back to anything close to normal, and dozens of companies are racing to develop vaccines. Experts agree that more than one vaccine will be needed, because no single company could produce the billions of doses needed.

“None of us are safe unless all of us are safe,” said Dr. Angela Rasmussen, a virologist at Columbia University in New York. “It’s not just us. It’s everybody in the world.”

The Moderna vaccine uses genetic material from the virus, called mRNA, to prompt the immune system to fight the coronavirus.

The report Tuesday confirmed and provided details on findings the company announced May 18 in a news release that was criticized for lacking data. Moderna defended itself at the time, saying that as a publicly traded company it had a legal obligation to disclose results that could affect its share price, and that the actual data would be published later.

The results are from an early Phase 1 study that was designed to test low, medium and high doses of the vaccine and to gauge their safety and ability to create immunity to the virus. The participants were 45 healthy adults, ages 18 to 55, who received two vaccinations 28 days apart.

After the second shot, all of the participants developed so-called neutralizing antibodies, which can inactivate the virus in lab tests. The levels of those antibodies were similar to those in the upper range in patients who had recovered from coronavirus infections. The vaccine also produced a favorable response involving T-cells, another part of the immune system.

“It exceeds all expectations,” said Dr. Kizzmekia S. Corbett, a viral immunologist and leader of a team that developed the vaccine at the infectious disease institute.

More than half of the participants had side effects, including fatigue, chills, headaches, muscle aches and pain at the injection site. Some had fever. One person who received the low dose developed hives and was withdrawn from the study. None of the side effects were considered serious.

Experts not involved with the study said the results were encouraging, but early. “Just because you have antibodies doesn’t mean you’re completely immune,” Rasmussen said.

It is possible, she said, that a vaccine might not totally prevent infection, but that it might make the illness less severe. “If it’s a choice between a bad cold and being on a ventilator, I’ll take the bad cold,” she said.

Dr. Paul Offit, an infectious disease expert at the University of Pennsylvania and Children’s Hospital of Philadelphia, said that the neutralizing antibodies and other immune responses were a good sign, but that it was not known yet whether they would actually protect people against the virus, or how long they would last. The side effects were a “small price to pay” for protection against a potentially severe disease, he said, though fever may be a cause for concern once the vaccine is given to large numbers of people.

“You always worry that fever, especially high fever, could lead to other things,” Offit said, adding that only a large controlled study can determine whether the vaccine is truly safe and effective.

Otherwise, “it’s reading the tea leaves,” he said. “You just don’t know anything until you do a Phase 3 trial.”