On May 18, 2020, Moderna, Inc. of Cambridge, Massachusetts announced that it had obtained “positive interim clinical data” from a Phase I human clinical trial of its experimental mRNA-1273 COVID-19 vaccine that began on Mar. 16. The biotechnology company said that eight of the 45 healthy adult volunteer trial subjects developed antibodies that may provide protection from the SARS-CoV-2 virus that causes COVID-19.1 2 3 The company also reported that four participants suffered Grade 3 vaccine reactions.
Moderna’s chief medical officer Tal Zaks, MD said:
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. 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.
Severe Adverse Events Reported After One or Two Vaccine Doses
Each of the 45 participants was given two doses of the Moderna vaccine about a month apart. The dosage levels were 25, 100 or 250 micrograms (µg). Moderna said that the four participants who received doses of 25 µg developed antibodies against SARS-Cov-2 about two weeks after the second dose was administered and that the same was true for the four participants given doses of 100 µg. The company noted that the vaccine was “generally safe and well tolerated.”1 2
The mRNA-1273 vaccine reportedly produced a “Grade 3 adverse event” in one participant among those who received doses of between 25 µg and 100 µg doses. That person experienced Grade 3 erythema or a rash around the injection site. A Grade 3 rash can mean blistering, open ulcers, wet peeling (moist desquamation) or a serious rash over large areas of the body.4 5
Three participants in the clinical trial who received a vaccine dose of 250 µg doses experienced “Grade 3 systemic symptoms” following administration of the second dose. Moderna described these as the “most notable” of the adverse events and said that they had been “transient and self-resolving.”1 2
The U.S. Department of Health and Human Services (HHS) describes a Grade 3 adverse event as “severe or medically significant but not immediately life-threatening; hospitalization or prolongation of hospitalization indicated; disabling; limiting self care” such as “bathing, dressing and undressing, feeding self, using the toilet, taking medications.”6
Moderna said that none of the participants in the clinical trial experienced Grade 4 adverse events. HHS lists Grade 4 events as “life-threatening consequences; urgent intervention indicated.” It describes Grade 5 events as “death related to [adverse events].”1 6
Clinical Trial Report Sends Moderna’s Stock Price Higher But Some Doubt Significance of the Report
News of the results of the Phase I trial produced a 20 percent spike in the value of Moderna stock on May 18. According to Barron’s:
After the market close, Moderna took advantage of the stock surge, announcing a proposed public offering of $1.3 billion in shares. The company said that the offering would “fund working capital needs related to the manufacturing” of its COVID-19 vaccine, among other things.8
But some vaccine researchers have expressed concern about the limited nature of the Phase I trial data released by Moderna, as well as the manner in which it was made public. Professor Anna Durbin, MD of Johns Hopkins University’s Bloomberg School of Public Health said:
I do think it’s a bit of a concern that they haven’t published the results of any of their ongoing trials that they mention in their press release. They have not published any of that. I would like to see the data to make my own interpretation of the data.7
John Rose, MD, professor emeritus of pathology at Yale University, said, “My guess is that their numbers are marginal or they would say more.”7
1 Press Release. Moderna Announces Positive Interim Phase 1 Data for its mRNA Vaccine (mRNA-1273) Against Novel Coronavirus. Moderna, Inc. May 18, 2020.
2 Edwards E. Moderna’s COVID-19 vaccine shows positive results, moves to larger studies. NBC News May 18, 2020.
3 Neergaard L, Johnson CK. AP Exclusive: Coronavirus vaccine test opens with 1st doses. Associated Press Mar. 16, 2020.
4 i-Base. How side effects are graded.
5 Wikipedia. Moist desquamation.
6 U.S. Department of Health and Human Services. Common Terminology Criteria for Adverse Events (CTCAE). Nov. 27, 2017.
7 Branswell H. Vaccine experts say Moderna didn’t produce data critical to assessing Covid-19 vaccine. STAT May 19, 2020.
8 Nathan-Kazis J. Moderna’s Stock Has Tripled on Vaccine News. How to Tell if It’s Worth the Money. Barron’s May 19, 2020.