Interim results of Moderna’s phase-1 human clinical trial of novel coronavirus vaccine (mRNA-1273) shows the vaccine is safe. The vaccine was also able to elicit neutralizing antibodies.

Interim results of Moderna’s phase-1 human clinical trial of novel coronavirus vaccine (mRNA-1273) that uses messenger RNA (mRNa) shows the vaccine is safe. The vaccine was also able to elicit neutralizing antibodies at day 43 (two weeks after the second dose). The level of neutralizing antibodies produced was at or above levels generally seen in the plasma of people who have recovered for COVID-19 disease.

Three different dosages — 25 microgram, 100 microgram and 250 microgram — were tested and two doses of each vaccine were administered to health volunteers. The vaccine given to participants aged 18 to 55 years. Interim results of four participants each who received two doses of 25 microgram and 100 microgram dosages of the vaccine were available.

Safety of the vaccine

According to Moderna, the vaccine at 25 microgram, 100 microgram was “generally safe and well tolerated”. While no serious adverse events were seen in both dosages, and one volunteer who received 100 microgram dosage of the vaccine developed redness at the site of injection. All three participants who received 250 microgram of the vaccine developed redness at the injection site.

“All adverse events have been transient and self-resolving. No grade four adverse events or serious adverse events have been reported,” the company said in a statement.

Immune responses

Phase-1 trial mainly evaluates the safety of the vaccine. The ability of the vaccine to elicit immune response is also looked for. After two doses, the level of neutralizing antibodies increased in a dose-dependent manner and is similar to or higher than in people who have recovered from COVID-19 disease.

Based on the interim Phase 1 data, the phase-2 study will be amended to study only two dose levels, 50 µg and 100 µg, the company said.

The company has already secured permission from FDA to carry out a phase-2 trial of the vaccine. Only phase-2 and phase-3 trials can provide evidence about the efficacy of the vaccine.

“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,” said Stéphane Bancel, Chief Executive Officer at Moderna said in the release. “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 from SARS-CoV-2.”

Development of the vaccine

The vaccine was developed by the U.S. National Institute of Allergy and Infectious Diseases (NIAID) scientists and their collaborators at the biotechnology company Moderna, Inc., based in Cambridge, Massachusetts. The Coalition for Epidemic Preparedness Innovations (CEPI) supported the manufacturing of the vaccine candidate for the Phase-1 clinical trial.

This vaccine has lipid nanoparticle-encapsulated mRNA that codes for the full-length prefusion stabilised spike (S) protein. Unlike usual vaccines, RNA vaccines work by introducing an mRNA sequence into the host’s cells. This mRNA codes for a disease specific antigen, which in this case is the spike protein, and once inside a cell, it instructs the cell to produce the antigen, which is recognised by the immune system, and makes an antibody or cellular response.