Safe COVID-19 experimental vaccine, generates immune response

An investigational vaccine, mRNA-1273, designed to protect against SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), was generally well tolerated and caused neutralizing antibody activity in healthy adults, according to provisional results published online today in The New England Journal of Medicine. The ongoing phase 1 trial is supported by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health. The experimental vaccine is being jointly developed by researchers at NIAID and Moderna, Inc. of Cambridge, Massachusetts. Manufactured by Moderna, mRNA-1273 is designed to induce neutralizing antibodies to a portion of the coronavirus “spike” protein, which the virus uses to bind to and enter human cells.

The trial was led by Lisa A. Jackson, MD, MPH, of the Kaiser Permanente Washington Health Research Institute in Seattle, where the first participant received the candidate vaccine on March 16. This interim report details the initial findings of the first 45 participants, ages 18 to 55, enrolled at study sites in Seattle and at Emory University in Atlanta. Three groups of 15 participants received two intramuscular injections, 28 days apart, of 25, 100, or 250 micrograms (mcg) of the investigational vaccine. All participants received an injection; 42 received both scheduled injections.

In April, the trial was expanded to enroll adults 55 and older; now it has 120 participants. However, the recently published results cover only the age group of 18 to 55 years.

Regarding safety, no serious adverse events were reported. More than half of the participants reported fatigue, headache, chills, myalgia, or pain at the injection site. Systemic adverse events were more common after the second vaccination and in those who received the highest dose of vaccine. Data on side effects and immune responses in various doses of vaccines reported the doses used or planned for use in Phase 2 and 3 clinical trials of the investigational vaccine.

The interim analysis includes test results that measure the levels of neutralizing activity induced by the vaccine up to day 43 after the second injection. Two doses of the vaccine elicited high levels of neutralizing antibody activity that were above the average values ​​observed in convalescent sera obtained from people with COVID-19 confirmed disease.

A phase 2 clinical trial of mRNA-1273, sponsored by Moderna, began enrollment in late May. Plans are underway to launch a Phase 3 efficacy test in July 2020.