Moderna Reports Positive Early Data for COVID-19 Vaccine Candidate


Moderna’s coronavirus disease 2019 vaccine candidate, mRNA-1273, showed promise in interim data from its phase 1 study.


Moderna announced new interim clinical data results for its coronavirus disease 2019 (COVID-19) vaccine candidate from a phase 1 study.

The investigational vaccine, called mRNA-1273, was launched in volunteers on March 16, making it the first trial to be started in humans for a vaccine for this virus. The study is funded by the National Institute of Allergy and Infectious Diseases.

Related: A Flurry of COVID-19 Studies Are Underway, but Scientists Warn a Vaccine Will Take Time

According to Moderna, immunogenicity data are currently available for the 25 µg and 100 µg dose level (ages 18 to 55) after 2 doses (day 43) and at the 250 µg level (ages 18 to 55) after 1 dose (day 29). Across all 3 dose levels, and between prime and boost within the 25 µg and 100 µg dose levels, dose dependent increases in immunogenicity were observed. All participants ages 18 to 55 across all 3 dose levels seroconverted by day 15 after a single dose. At day 43, 2 weeks following the second dose, at the 25 µg dose level, levels of binding antibodies were at the levels seen in blood samples from individual who have recovered from COVID-19 (convalescent sera) tested in the same assay. At day 43, at the 100 µg dose level, levels of binding antibodies significantly exceeded the levels seen in convalescent sera. Samples are not yet available for remaining participants.

Neutralizing antibody data are currently only available for the first 4 participants in the study in each of the 25 µg and 100 µg dose level cohorts. The vaccine elicited neutralizing antibodies in all 8 of these participants, as measured by plaque reduction neutralization assays against live severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The levels of neutralizing antibodies at day 43 were at or above levels generally seen in convalescent sera, according to Moderna.

The phase 1 study involves 45 volunteer participants evaluating mRNA-1273 over a 6-week period. Study participants include healthy adults ages 18 to 55 years old living in the Seattle, Washington area. Based on these findings, the phase 2 portion of the study will be amended to study 2 dose levels, 50 µg and 100 µg, with the aim of selecting a dose for pivotal studies. Additionally, preclinical results from a viral challenge study in mice are also available, showing that vaccination with mRNA-1273 prevented viral replication in the lungs of animals challenged with SARS-CoV-2.

“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,” Tal Zaks, MD, PhD, chief medical officer at Moderna, said in a statement. “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.”

According to the early results, mRNA-1273 demonstrated a safety profile consistent with that seen in prior Moderna infectious disease vaccine clinical studies.

Moderna expects to begin its phase 3 study in July 2020, according to the press release.



1. Moderna Announces Positive Interim Phase 1 Data for its mRNA Vaccine (mRNA-1273) Against Novel Coronavirus. News Release. Moderna; May 18, 2020. Accessed May 18, 2020.

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