Moderna Begins Trial for Omicron-Specific Booster Vaccine

Company announced it had administered its first shot to a participant for its extension of an earlier phase 2 study.

Moderna announced it has begun its phase 2 clinical trial extension for its Omicron-specific booster (mRNA-1273.529) vaccine candidate yesterday.

This is an extension of an earlier study that will evaluate the immunogenicity, safety, and reactogenicity of mRNA-1273.529 as a single booster dose in adults aged 18 years and older.

The company’s Omicron-specific booster candidate will include 2 cohorts:

  • One including participants who received the two-dose primary series of mRNA-1273;
  • And a second group for participants who received the 2-dose primary series and a 50 µg booster dose of mRNA-1273

"We are reassured by the antibody persistence against Omicron at 6 months after the currently authorized 50 µg booster of mRNA-1273,” Moderna CEO Stéphane Bancel, said. “Nonetheless, given the long-term threat demonstrated by Omicron's immune escape, we are advancing our Omicron-specific variant vaccine booster candidate and we are pleased to begin this part of our Phase 2 study."

In a recently published study, Moderna was shown to be more efficacious at preventing breakthrough infections and hospitalizations than the Pfizer-BioNTech vaccine. It is important to note that the study period was from July to November 2021 when the Delta variant was still the predominant strain in the US.

The Moderna recipients had a significantly lower risk of breakthrough infections than Pfizer-BioNTech recipients. Sixty days after vaccination, the hospitalization risk was 12.7% for the Moderna cohort and 13.3% for the Pfizer recipients.

The Centers for Disease Control and Prevention said that the Omicron is now accounting for 99.9% of the cases in the US. And, in a world where the Omicron variant is now the dominant strain, Moderna is weighing its booster strategies.

"We are also evaluating whether to include this Omicron-specific candidate in our multivalent booster pro.” Bancel said. “We will continue to share data with public health authorities to help them make evidence-based decisions on the best booster strategies against SARS-CoV-2."