Moderna’s Covid-19 Vaccine: Positive Preliminary Safety & Efficacy Data

Jennifer Hudson
January 10, 2020

Exciting preliminary data and news from Moderna Therapeutics regarding the safety and efficacy of the mRNA-1273 vaccine against SARS-CoV-2 (

Moderna’s vaccine is a messenger RNA (mRNA) that codes for the virus spike (S) protein. After injection, this mRNA vaccine enters the patients’ cells, where it manufactures the S protein, which will trigger the immune system to be activated and develop antibodies.

Today (05/18/20), Moderna announced positive interim data of mRNA-1273 against the coronavirus from a phase I clinical trial study, which was led by the National Institute of Allergy & Infectious Diseases (NIAID). Immunogenicity data are available for participants receiving two doses of 25ug and 100ug and also in participants receiving one dose of 250ug. Interestingly, the study showed dose-dependent increases in immunogenicity across all the three dose levels. Also, all participants (three dose levels) seroconverted by day 15 after a single dose. Two weeks following the second dose, at the 25µg dose level, levels of the antibodies were at the levels seen in convalescent sera, which are the blood samples from patients who recovered from the coronavirus. At the same day, at the 100µg dose level, levels of the antibodies exceeded the levels seen in convalescent sera. It is important to mention that Moderna has available neutralizing antibody data only for the first four participants in each of the 25µg and 100µg dose level cohorts and all of them developed neutralizing antibodies against coronavirus. Thus, based on these important preliminary findings, Moderna will amend its phase II clinical trial to study the 50ug and 100ug dose levels. Moderna’s executives anticipate to be able to initiate a phase III clinical trial on July.

Overall, these are exciting and promising data, however we should be cautious, since they are based on very few individuals, who were healthy and relatively young. Furthermore, the safety data are preliminary, since it usually takes several years to collect and evaluate data for traditional vaccine development. We are looking forward to the complete phase I data analysis and also the preliminary data from the phase II clinical trial. In addition to Moderna, Johnson & Johnson has already identified a lead covid-19 vaccine candidate, which will move to human phase I clinical trial on September 2020.