Moderna Initiates Phase 2 Study of Omicron-Specific Booster Vaccine


Moderna expects to enroll approximately 375 participants in about 20 sites across the United States.

Moderna said that the first individual in the phase 2 study of the company’s COVID-19 Omicron-specific bivalent booster candidate (mRNA-1273.214), which combines the Moderna COVID-19 vaccine (mRNA-1273) and the Omicron-specific booster candidate (mRNA-1273.529), has been administered the vaccine candidate.

"Our mRNA platform allows us to pivot with speed and flexibility to create a bespoke vaccine to target new variants as they arise," Stéphane Bancel, CEO of Moderna, said in a statement. "Our goal has been to remain ahead of the virus, and we are committed to generating and sharing data with public health authorities as they prepare for the fall booster season.”

The study is an extension of an earlier one that aimed to evaluate the immunogenicity, reactogenicity, and safety of mRNA-1273.214 as a single-booster dose in adults aged 18 years and older who previously received the 2-dose primary series of mRNA-1273 and a booster of the same vaccine in the 50-µg strength at least 3 months ago.

Moderna expects to enroll about 375 individuals at approximately 20 different sites across the United States. Additionally, Moderna is also evaluating the Omicron-specific booster in a phase 2 study within the United States.

The company will also evaluate the Omicron-specific booster in a separate phase 3 study in the United Kingdom in collaboration with the National Institutes for Health Research. Moderna hopes to begin dosing with mRNA-1273.214 in the study soon.

The Omicron variant has been the dominant variant in the United States since December 20, 2021, according to the CDC. The variant was first reported to the World Health Organization on November 24, 2021, in Botswana and South Africa. On December 1, 2021, the first case of the Omicron variant was confirmed in the United States.

Omicron can spread more easily than other variants, even if an individual is vaccinated. However, the Omicron infection causes less severe disease, though it is more infectious, according to the CDC.

Vaccinated individuals are more likely to experience a breakthrough infection but are still less likely to develop serious symptoms than those who are unvaccinated.

The CDC still recommends getting vaccinated, using masks dependent on the COVID-19 risk in the local community and when and individual is sick or caring for someone else who is sick. Studies continue to determine the viral characteristics of the Omicron variant, according to the CDC.


  1. Moderna announces first participant dosed in phase 2 study of Omicron-specific bivalent booster candidate. Moderna. News release. March 10, 2022. Accessed March 15, 2022.
  2. Centers for Disease Control and Prevention. Omicron variant: what you need to know. Updated February 2, 2022. Accessed March 15, 2022.
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