COVID-19 Vaccine Candidate mRNA-1273 Reports Interim Phase 1 Data

Investigators report comparable SARS-CoV-2 neutralizing antibody counts across age groups, as well as favorable safety outcomes for the two-dose vaccine.

New interim data from the phase 1 assessment of investigative coronavirus 2019 (COVID-19) vaccine candidate mRNA-1273 showed the two-dose vaccine has tolerance across age groups and capability in inducing neutralizing antibodies in the upper-half range of convalescent serum across observed age strata.

The interim dose-ranging data, presented by Jacqueline M. Miller, MD, during the Advisory Committee on Immunization Practices (ACIP) August Meeting today, evidences two-dose 100mcg administration of the Moderna vaccine candidate for comprehensive pseudovirus neutralization, response titers comparable across age groups, and generally favorable tolerability and safety profiles thus far.

The phase 1 trial, sponsored by the National Institutes of Health, enrolled 120 healthy adults aged ≥18 years old. For the sake of observing immunogenicity, safety, and tolerability across age groups, participants were stratified by ages 18-55 (n = 45), 56-70 (20) for two-dose administration of 25 and 100 mcg mRNA-1273, and all ages (35) for one-dose 50 mcg.

Investigators are assessing for immunogenicity endpoints, per Enzyme-linked immunosorbent assay (ELISA), pseudo neutralization, live virus neutralization, and intracellular cytokine straining assay.

They’re also assessing for safety endpoints, per adverse reaction at 7 days post-injections, unsolicited adverse events at 28 days post-injections, and serious adverse events.

Per previous findings, 100mcg dose was selected due to having comparable neutralizing antibody titers to 250mcg, but an improved safety profile.

Currently through the phase 1 assessment, no vaccine-related serious adverse events have been reported among the 120 participants. Systemic symptoms following the first dose have been mostly mild in severity, with fatigue and injection site pain being the most frequently reported. The second dose’s symptoms are moderate in severity.

Myalgia, headache, chills, and fever have been more frequently reported after the second dose.

Per ELISA, SARS-CoV-2 neutralizing antibody counts have been comparable across participant age groups and to convalescent sera out to day 57 post-second dose, investigators reported.

The vaccine has been shown to induce CD4+ T-cells of the Th-1 phenotype within 14 days post-second dose across all age groups.

The phase 2a and 3 trials for mRNA-1273 are underway, with participant populations escalating to 600 then 30,000 adults, respectively. The overall goal of the phase 3 trial is to demonstrate efficacy of the candidate in preventing COVID-19, and to observe the safety and reactogenicity of a two-dose vaccination 28 days apart.