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Experimental COVID-19 Vaccine Generates Immune Response, Deemed Safe in Phase I Trial


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According to a press release from the National Institutes of Health, an investigational vaccine designed to protect against SARS-CoV-2, the virus that causes COVID-19—mRNA-1273—was generally well tolerated and prompted neutralizing antibody activity in healthy adults. These interim results were published by Jackson et al in The New England Journal of Medicine.

The ongoing phase I trial is supported by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health. The experimental vaccine is being codeveloped by researchers at NIAID and Moderna, Inc. Manufactured by Moderna, mRNA-1273 is designed to induce neutralizing antibodies directed at a portion of the coronavirus “spike” protein, which the virus uses to bind to and enter human cells.

“The mRNA-1273 vaccine induced anti–SARS-CoV-2 immune responses in all participants, and no trial-limiting safety concerns were identified. These findings support further development of this vaccine.”
— Jackson et al

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Study Participants

The trial was led by Lisa A. Jackson, MD, MPH, of Kaiser Permanente Washington Health Research Institute in Seattle, where the first participant received the candidate vaccine on March 16, 2020. This interim report details the initial findings from the first 45 participants, aged 18 to 55, enrolled at the study sites in Seattle and at Emory University in Atlanta.

Three groups of 15 participants received two intramuscular injections, 28 days apart, of either 25, 100, or 250 μg of the investigational vaccine. All the participants received one injection; 42 received both scheduled injections.

In April, the trial was expanded to enroll adults older than 55; it now has 120 participants. However, the newly published results cover the 18- to 55-year age group only.

Early Results

Regarding safety, no serious adverse events were reported. More than half of the participants reported fatigue, headache, chills, myalgia, or pain at the injection site. Systemic adverse events were more common following the second vaccination and in those who received the highest vaccine dose. Data on side effects and immune responses at various vaccine dosages informed the doses used or planned for use in the phase II and III clinical trials of the investigational vaccine.

The interim analysis includes results of tests measuring levels of vaccine-induced neutralizing activity through day 43 after the second injection. Two doses of the vaccine prompted high levels of neutralizing antibody activity that were above the average values seen in convalescent sera obtained from persons with confirmed COVID-19 infection.

The study authors concluded, “The mRNA-1273 vaccine induced anti–SARS-CoV-2 immune responses in all participants, and no trial-limiting safety concerns were identified. These findings support further development of this vaccine.”

Next Steps

phase II clinical trial of mRNA-1273, sponsored by Moderna, began enrollment in late May. Plans are underway to launch a phase III efficacy trial in July 2020.

Additional information about the phase I clinical trial design is available at clinicaltrials.gov.

Disclosure: This trial was supported in part by the NIAID. Funding for the manufacture of mRNA-1273 phase I material was provided by the Coalition for Epidemic Preparedness Innovations. For full disclosures of the study authors, visit nejm.org.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
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