Moderna’s Coronavirus Vaccine Shows Promise

Biotechnology company Moderna announced Monday (May 18) that their experimental coronavirus vaccine showed promising results in an early trial known as a Phase I study.

According to a statement from Cambridge, Massachusetts-based Moderna, all 45 participants in the trial developed detectable levels of antibodies within 15 days after receiving a dose of the vaccine, called mRNA-1273.

The 45 participants were divided into three groups and received different doses of the vaccine: 25 micrograms (μg), 100 μg and 250 μg. Participants then received a second dose of vaccine about a month later. The higher the dose (or the second dose used in the first two groups), the more antibodies were produced, the researchers found.

Two weeks after the first group of 15 participants received the second 25-microgram dose of vaccine, their blood levels of antibodies were comparable to levels found in blood samples from people who had recovered from COVID-19. Those who received two doses of 100 micrograms of the vaccine had antibody levels that exceeded levels found in blood samples from people recovering from COVID-19. Samples from other participants are not yet available, according to the statement.

But this data only refers to levels of “binding” antibodies, or antibodies that can bind to the coronavirus but don’t necessarily attack it. But the researchers also collected data on “neutralizing” antibodies, or those that can block infection, from eight participants (data from the rest of the participants is also not yet available).

All eight participants (four received 25 micrograms and four received 100 micrograms) had neutralizing antibodies at or above the levels seen in people recovered from COVID-19. In another study on mice, similar neutralizing antibodies were found to prevent viral replication in mice infected with SARS-CoV-2.

In a statement, the company wrote that the vaccine was “generally safe and well tolerated” and that no participants experienced serious side effects.” All adverse events were short-lived and resolved on their own.” Some people had side effects such as redness and fever at the injection site, headache or flu-like symptoms, according to NPR.

Moderna’s vaccine uses a new technique that hasn’t been used in any approved vaccines so far: it uses a molecule called messenger RNA (mRNA) to instruct cells to build up viral proteins, specifically the coronavirus spikes that the virus uses to infect human cells. The idea is that the immune system will create antibodies that will recognize that spike protein and prevent the coronavirus from infecting the cell.

According to a previous report by Live Science, the U.S. Food and Drug Administration (FDA) recently gave Moderna the go-ahead to begin Phase 2 testing of its vaccine, which will involve testing on an additional 600 people. The company is aiming to begin their Phase 3 trial in July, where they will recruit hundreds to thousands more people to learn more about whether the vaccine works and whether participants have any adverse reactions, and will use this data to calculate the correct dose to give participants.

“These provisional Phase 1 data, while early, demonstrate that vaccination with mRNA-1273, starting with doses as low as 25 micrograms, can elicit the immune response elicited by natural infection,” said Dr. Tal Zaks, Moderna’s chief medical officer, in a statement. When combined with data from the mouse study, these results “confirm our belief that mRNA-1273 has the potential to prevent COVID-19 disease and advance our ability to select a dose for a pivotal trial.”