At day 43, two weeks following the second dose, at the 25 µg dose, levels of binding antibodies were at the levels seen in convalescent sera (blood samples from people who have recovered from COVID-19) tested in the same assay. At day 43, at the 100 µg dose, levels of binding antibodies significantly exceeded the levels seen in convalescent sera. Samples are not yet available for remaining participants.

At this time, neutralizing antibody data are available only for the first four participants in each of the 25 µg and 100 µg dose level cohorts. Consistent with the binding antibody data, mRNA-1273 vaccination elicited neutralizing antibodies in all eight of these participants, as measured by plaque reduction neutralization (PRNT) assays against live SARS-CoV-2.

The levels of neutralizing antibodies at day 43 were at or above levels generally seen in convalescent sera.

Moderna mRNA-1273 Safety 

mRNA-1273 was generally safe and well-tolerated, with a safety profile consistent with that seen in prior Moderna’s infectious disease vaccine clinical studies. The sole incidence of a grade 3 adverse event in the 25 µg and 100 µg dose cohorts was a single participant at 100 µg who experienced grade 3 erythema (redness) around the injection site. To date, the most notable adverse events were seen at the 250 µg dose level, comprising three participants with grade 3 systemic symptoms, only following the second dose. All adverse events have been transient and self-resolving. No grade 4 adverse events or serious adverse events have been reported.

Preclinical Results from Moderna and NIAID

Preclinical results from a viral challenge study in mice conducted in collaboration with NIAID and its academic partners are also available. In this study, vaccination with mRNA-1273 prevented viral replication in the lungs of animals challenged with SARS-CoV-2. Neutralizing titers in Phase 1 clinical trial participants at the 25 µg and 100 µg dose levels were consistent with neutralizing titers that were protective in the mouse challenge model.

Based on the interim Phase 1 data, the Moderna-led Phase 2 study will be amended to study two dose levels, 50 µg, and 100 µg, with the aim of selecting a dose for pivotal studies.

The NIAID-led Phase 1 study is being amended to include a 50 µg dose level cohort across each of the three age groups. Moderna anticipates the dose for the Phase 3 study to be between 25 µg and 100 µg and expects Phase 3 trial initiation in July, subject to finalization of the clinical trial protocol.

Tal Zaks, M.D., Ph.D., Chief Medical Officer at Moderna 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.”

Conference Call and Webcast Information

Moderna is currently hosting a live conference call and webcast at 8:30 a.m. ET on Monday, May 18, 2020. To access the live conference call, dial 866-922-5184 (domestic) or 409-937-8950 (international) and refer to conference ID 2186342. A webcast of the call will also be available under “Events and Presentations” in the Investors section of the Moderna website at investors.modernatx.com. The archived webcast will be available on Moderna’s website approximately two hours after the conference call.

Prohost Observations

This is great news. We congratulate Moderna’s scientists and the whole world because we will all benefit. We also congratulate those who never lost hope and never have been affected by fear and pessimism.

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