In May 2020, experts in vaccine field lodged criticism against mRNA 1273 on ground of lack of sufficient data of the candidate to support the development of the vaccine for the treatment of COVID-2019 infections. Barbuto & Johansson, P.A. (“BARJO”) and Of Counsel, Neil Rothstein, Esq. has initiated an investigation into Moderna Therapeutics on behalf of investors as to whether Moderna and certain of its officers and/or directors have engaged in fraud, negligence or other unlawful business practices. The "reason for caution" cited was lack of immune response data for 37 participants in a phase I trial which was evaluating the safety and immunogenicity of mRNA 1273, in healthy volunteers. On Monday, 18 May 2020, Moderna shared that 8 out of 45 participants in its COVID-19 vaccine study developed neutralizing antibodies  .
In May 2020, Moderna Therapeutics in collaboration with Biomedical Advanced Research and Development Authority initiated a phase II trial to evaluate the safety, reactogenicity, and immunogenicity of 2 doses of mRNA 1273 vaccine for prevention of COVID-2019 infections in adults 18 years of age or older (mRNA-1273-P201; 75A50120C00034; NCT04405076). The randomised, observer-blind, placebo controlled, dose-confirmation study will enrol approximately 600 volunteers in the US  . By the end of May 2020, first participants in each age cohort had been dosed in the trial  .
In May 2020, the US FDA granted a fast track designation to mRNA 1273 for prevention of COVID-2019 infections  .
As of May 2020, Moderna Therapeutics was finalising the protocol for a planned phase III trial   .
As of May 2020, US FDA approved Investigational New Drug (IND) application of mRNA 1273 for initiating a phase II trial in prevention of COVID-2019 infections. In the same month, Moderna received initial feedback from the US FDA regarding design of the planned phase II study. Earlier, in April 2020, Moderna Therapeutics submitted an IND application for the same    .
In March 2020, National Institute of Allergy and Infectious Diseases dosed its first patient and initiated a phase I trial to evaluate the safety and immunogenicity of mRNA 1273, in healthy volunteers (1UM1AI148373-01; 20-0003; NCT04283461).The primary objective is to evaluate the safety and reactogenicity of a two-dose vaccination schedule of mRNA-1273. The secondary objective is to evaluate the immunogenicity to the SARS-CoV-2 S protein. As of April 2020, enrolment of 3 dose cohorts (25 µg, 100 µg and 250 µg) was completed with 45 adults (aged 18 to 55) in the US. However as per the latest amended protocol by NIH, enrolment was underway in additional six cohorts (60 participants) that included three cohorts of 30 older adults (aged 56-70) and three cohorts of 30 elderly adults (aged 71 and above). Favourable interim results from the 25 µg and 100 µg cohorts were released in May 2020. Based on these results, the trial is proposed to be amended to include two dose levels, 50 µg and 100 µg, to select a dose for pivotal studies. A 50 µg dose level cohort will be included across each of the three age groups      .
In May 2020, Moderna reported favourable preclinical data from a mouse challenge model of COVID-2019 infections  .
In May 2020, Moderna Therapeutics announced an underwritten public offering of $US1.25 billion in shares of its common stock with a 30 day purchase option of an additional $US187.5 million. The net proceeds will be utilized for manufacturing of mRNA 1273 
In January 2020, Moderna Therapeutics announced that Coalition for Epidemic Preparedness Innovations (CEPI) will be funding the manufacture of an mRNA vaccine against COVID-2019 infections  .