U.S. biotechnology firm Moderna Inc. announced the results of its phase I clinical trial on May 18 on their promising vaccine candidate called mRNA-1273. Out of all the 76 vaccine contenders listed by the World Health Organisation (WHO), this is the first RNA vaccine trial to initiate an immune response by making antibodies to fight against the induced SARS-CoV-2 spike protein.
The preliminary study consisted of 45 healthy adult participants who were given different doses of the potential mRNA-1273 vaccine shot: a low dose of 25 micrograms and a medium dose of 100 micrograms. From them, eight people who were given 100 micrograms produced large amounts of antibodies equal to and sometimes exceeding the volume of antibodies developed by COVID-19 patients themselves. The details of the trial have not been made public yet as the experiment is on-going.
Researchers were able to establish that the vaccine candidate is safe because the only side effects seen were redness and soreness in one subject. Three other subjects given comparatively higher doses displayed fever, muscle pain and headaches as side effects, all of which disappeared after 24 hours, causing no other complications. The Food and Drugs Administration (FDA) has put the clinical trial on the fast-track route for emergency purposes. The agency gave the Massachusetts-based biotech company approval to start phase II of the trial with 600 healthy subjects.
While the phase I study was conducted on people aged between 18 to 55, the next phases will involve people aged 55 and older. Participants will be recipients of prime and booster vaccinations, of 50 microgram dosage or a 250 microgram dosage, with a gap of 28 days. Some of the participants will be then injected with a placebo to compare the efficacy of the mRNA-1273 vaccine.
Phase III of this promising RNA-based vaccine being developed in collaboration with National Institute of Allergy and Infectious Diseases (NIAID) is scheduled to begin in July, provided it passes phase II.
“While a commercially-available vaccine is not likely to be available for at least 12-18 months, Moderna reported it is possible that under emergency use, a vaccine could be available to some people, possibly including healthcare professionals, in the fall of 2020,” a statement made by the company in March reads.
Scientists at Moderna and NIAID got to work immediately after the genetic sequence of the virus was published online by Chinese researchers. In the past, the two collaborators were in the course of developing vaccines to treat Middle East Respiratory Syndrome (MERS), that has similar coronavirus spike proteins. These experiences enabled them to start testing the new vaccine on February 25.
Simultaneously, Moderma tested the vaccine on mice who were injected with the vaccine candidate and later infected with SARS-CoV-2 virus to observe how their bodies reacted. It was found the virus stopped multiplying in the lungs. The mice also produced antibodies as much as people who were given the vaccine in the first trial.
However, scientists remain skeptical about the drug’s effectiveness as it does not activate T cells. They are unclear if the antibody response will be enough to completely ward off COVID-19.
How was this vaccine made from mRNA technology? From the genetic sequence of SARS-CoV-2, the mRNA from bits of the spike protein is injected into a person, who will then start to produce the viral protein in the body. The person’s immune system then builds its defense mechanism against the protein by producing antibodies. In the future, this could prevent the spike from multiplying the virus if the person comes in contact with it.