The 50 µg booster dose of Moderna's existing mRNA-1273 vaccine is the same dosage currently authorised in the US and other jurisdictions, and is the same vaccine used for the primary two-dose series.
The company also tested a larger 100 µg dose of mRNA-1273, which increased neutralizing antibody levels approximately 83-fold compared to pre-boost levels.
On the back of these results, the mRNA-1273 booster will remain the ‘first line of defense’ against Omicron, says Moderna, particularly given the rapid spread of Omicron and the complexities in deploying a new vaccine. It will, however, also continue to evaluate a booster candidate specifically against the variant (mRNA-1273.529).
“The dramatic increase in COVID-19 cases from the Omicron variant is concerning to all. However, these data showing that the currently authorized Moderna COVID-19 booster can boost neutralizing antibody levels 37-fold higher than pre-boost levels are reassuring,” said Stéphane Bancel, CEO, Moderna.
“To respond to this highly transmissible variant, Moderna will continue to rapidly advance an Omicron-specific booster candidate into clinical testing in case it becomes necessary in the future. We will also continue to generate and share data across our booster strategies with public health authorities to help them make evidence-based decisions on the best vaccination strategies against SARS-CoV-2.”
The booster data includes sera from 20 booster recipients each of mRNA-1273 at the 50 µg and 100 µg dose levels, multivalent candidate mRNA-1273.211 at the 50 µg and 100 µg dose levels, and multivalent candidate mRNA-1273.213 at the 100 µg dose level.
Neutralizing antibodies against Omicron were assessed in a pseudovirus neutralization titer (ID50) assay (PsVNT) conducted at laboratories established by the National Institute of Allergy and Infectious Diseases’ (NIAID) Vaccine Research Center and Duke University Medical Center. A preprint submission is being prepared based on the data.
All groups had low neutralizing antibody levels in the Omicron PsVNT assay prior to boosting. At day 29 post boost, the authorized 50 µg booster of mRNA-1273 increased neutralizing geometric mean titers (GMT) against Omicron to 850, which is approximately 37-fold higher than pre-boost levels.
At day 29 post boost, the 100 µg dose booster of mRNA-1273 increased neutralizing GMT to 2228, which is approximately 83-fold higher than pre-boost levels. The multivalent candidates boosted Omicron specific neutralizing antibody levels to similarly high levels at both the 50 µg and 100 µg levels.
Fellow mRNA vaccine producers Pfizer/BioNTech announced earlier this month that a booster shot provided protection against Omicron in an initial study.