Amid surge in COVID-19 cases, ‘encouraging’ early data on vaccine candidate
Phase 1 trial results from the first COVID-19 vaccine candidate given to people in the United States showed that it induced anti-SARS-CoV-2 immune responses in all participants, according to a preliminary report published today.
The vaccine candidate, mRNA-1273, was developed by researchers from the National Institute of Allergy and Infectious Diseases and Moderna, Inc. The first trial participants were vaccinated on March 16, just over 2 months after the SARS-CoV-2 genome was posted publicly.
“Experience with the mRNA platform for other candidate vaccines and rapid manufacturing allowed the deployment of a first-in-human clinical vaccine candidate in record time,” researchers wrote in The New England Journal of Medicine. “Product development processes that normally require years were finished in about 2 months.”
The phase 1 dose-escalation, open-label trial enrolled 45 healthy adults between the ages of 18 and 55 years. The researchers assigned three groups of 15 participants to receive two vaccinations 28 days apart in a dose of either 25 µg, 100 µg or 250 µg.
After the first vaccination was administered, the researchers found that antibody responses were higher with the higher dose, with day 29 enzyme-linked immunosorbent assay anti-S-2P antibody geometric mean titers (GMT) of 40,277 in the 25-µg group, 109,209 in the 100-µg group and 213,526 in the 250-µg group. Following the second vaccination, GMT levels increased to 299,751 in the 25-µg group, 782,719 in the 100-µg group and 1,192,154 in the 250-µg group at day 57.
The researchers reported detecting serum-neutralizing activity in every participant evaluated following the second vaccination “with values generally similar to those in the upper half of the distribution of a panel of control convalescent serum specimens.”
They recorded adverse events such as fatigue, chills, headaches, myalgia and pain at the injection site in more than half of participants.
“Systemic adverse events were more common after the second vaccination, particularly with the highest dose, and three participants in the 250-µg dose group reported one or more severe adverse events,” the researcher wrote.
They noted that a phase 2 trial testing 50-µg and 100-µg doses of vaccine has already begun, and a phase 3 trial that will evaluate 100-µg doses is expected to begin this summer.