Positive interim clinical data of the mRNA-1273 vaccine (Moderna, Inc) against the coronavirus disease 2019 (COVID-19) were reported from a phase 1 study led by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH). 

Data are currently available for the 25 µg and 100 µg dose level, ages 18-55 years, after 2 doses at day 43, and at the 250 µg level, ages 18-55 years, after 1 dose at day 29. Dose dependent increases in immunogenicity were seen across the 3 dose levels and between prime and boost within 25 µg and 100 µg levels, according to a Moderna press release.

All participants across the 3 dose levels seroconverted by day 15 after a single dose. At day 43 at the 25 µg dose level, levels of binding antibodies were at the levels seen in convalescent sera, or blood samples from those who have recovered from COVID-19, tested in the same assay. At day 43 at the 100 µg dose, levels of binding antibodies significantly exceeded the levels seen in convalescent sera. Samples are not yet available for remaining participants, according to the press release.

Neutralizing anitbody data are available only for the first 4 participants in each of the 25 µg and 100 µg dose level cohorts, and the mRNA-1273 vaccination elicited neutralizing antibodies in all 8 of these participants, according to the study authors. The levels of neutralizing antibodies shown at day 43 by researchers were at or above levels generally seen in convalescent sera. 

mRNA-1273 was safe and well-tolerated, with a sole incidence of a grade 3 adverse event (AE) in the 25 µg and 100 µg dose cohorts reported in a single participant at 100 µg, who experienced grade 3 erythema around the injection site. The most notable AEs were seen at the 250 µg dose level, comprising 3 participants with grade 3 systemic symptoms only following the second dose. No grade 4 AEs or serious AEs have been reported, according to the press release. 

Based on the interim phase 1 data, the phase 2 study will be modified to study 2 dose levels, 50 µg and 100 µg, with the aim of selecting a dose for pivotal studies, according to the study authors. Further, Moderna is planning on a dose for a phase 3 study to be between 25 µg and 100 µg, with hopes of beginning trial initiation in July.

“These interim phase 1 data, while early, demonstrate that vaccination with mRNA-1273 elicits an immune response of the magnitude caused by natural infection starting with a dose as low as 25 µg,” said Tal Zaks, MD, PhD, chief medical officer at Moderna, in the press release. “When combined with the success in preventing viral replication in the lungs of a pre-clinical challenge model at a dose that elicited similar levels of neutralizing antibodies, these data substantiate our belief that mRNA-1273 has the potential to prevent COVID-19 disease and advance our ability to select a dose for pivotal trials.”

Moderna Announces Positive Interim Phase 1 Data for its mRNA Vaccine (mRNA-1273) Against Novel Coronavirus [news release]. Cambridge, Mass.; Moderna: May 18, 2020. https://investors.modernatx.com/news-releases/news-release-details/moderna-announces-positive-interim-phase-1-data-its-mrna-vaccine. Accessed May 18, 2020.