A new mRNA vaccine candidate for COVID-19, mRNA-1273, developed by US Biotech major Moderna Inc, was found to induce immune response against the SARS-CoV-2 in all healthy participants involved in the study, revealed the findings published online in the New England Journal of Medicine.
The vaccine constitutes a lipid nanoparticle encapsulated nucleoside-modified messenger RNA (mRNA) that encodes the SARS-CoV-2 spike (S) glycoprotein stabilized in its prefusion conformation.
The S glycoprotein is the outer surface protein of the COVID virus that mediates host cell attachment and enables for viral entry. It is the primary vaccine target for many candidate SARS-CoV-2 vaccines. The vaccine thereby induces the cells in the body to produce an immune response against the virus particle to develop antibodies that protect an individual from acquiring COVID-19.
The phase 1 trial included 45 healthy adults (18 to 55 years of age) receiving two vaccinations of mRNA-1273, 28 days apart, at a dose of 25 μg, 100 μg, or 250 μg. There were 15 participants in each dose group. Of the three doses evaluated, the 100-μg dose elicited high neutralization responses and Th1-skewed CD4 T cell responses, coupled with a reactogenicity profile that is more favourable than that of the higher dose, noted the authors.
Adverse events after the second dose occurred in seven of the 13 volunteers who got the 25-microgram dose, all 15 participants who received the 100 microgram dose and all 14 who got the 250 microgram dose. In the highest-dose group, three patients had severe reactions such as fever, chills, headache or nausea. One of these had a fever of 103.28 Fahrenheit (39.6 C), noted the study.
However, the study found no serious adverse events and the vaccine produced “reasonably high” levels of virus-killing or neutralising antibodies said Dr Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases.
The vaccine has been developed by the U.S Biotech firm Moderna. The company began the testing of the vaccine on March 16, after the genetic sequence of the virus was released in January. The company had expanded the Phase 1 trial to include adults over 55, who are more at risk of serious disease.
A phase 2 trial of mRNA-1273 involving 600 healthy adults, evaluating doses of 50 μg and 100 μg, is ongoing, the details of which can be viewed under ClinicalTrials.gov number, NCT04405076. The company said it will follow the volunteers for a year to look for side effects and observe how long immunity lasts. Moderna expects to start a phase 3 trial involving 30,000 volunteers on July 27.