Moderna, Inc. announced Health Canada has authorized the use of its BA.4/BA.5 Omicron-targeting bivalent COVID-19 booster vaccine, mRNA-1273.222, as a booster dose for active immunization against COVID-19 caused by the SARS-CoV-2 virus in individuals 18 years of age and older. The 50 µg booster dose of mRNA-1273.222 includes 25 µg of mRNA encoding for the spike protein of BA.4/BA.5 and 25 µg encoding for the original strain of the SARS-CoV-2 virus. Health Canada's authorization of mRNA-1273.222 was based both on pre-clinical data for mRNA-1273.222 as well as clinical data from a Phase 2/3 trial studying mRNA-1273.214.

A Phase 2/3 clinical trial for mRNA-1273.222 is fully enrolled and currently underway, with initial data expected later this year. mRNA-1273.222 is the second Moderna bivalent COVID-19 vaccine approved by Health Canada, following the approval of mRNA-1273.214 (SPIKEVAXBivalent) in September. Clinical trial data showed that a booster dose of mRNA-1273.214 increased neutralizing geometric mean titers against Omicron BA.1 approximately 8-fold above baseline levels.

Additional data showed that the higher antibody titers were sustained ninety days after administration. In addition, mRNA-1273.214 demonstrated significantly higher neutralizing antibody responses against Omicron BA.4/BA.5 compared to mRNA-1273 28 days after administration. Potent responses were also seen against Omicron BA.2.75 28 days after administration, suggesting that the bivalent booster elicits broad cross-neutralization against Omicron variants.