On Nov. 15, 2022, Moderna reported findings from a Phase II/III clinical trial where bivalent Omicron-targeting booster candidates, mRNA-1273.214 and mRNA-1273.222, met the primary endpoint of superiority against Omicron BA.4/BA.5 variants versus the mRNA-1273 booster. mRNA-1273 is the prototype vaccine of the company. 

According to the trial findings, both bivalent shots met non-inferiority immunogenicity criteria to the initial SARS-CoV-2 strain.

In 511 subjects aged 19 to 89 years, who were vaccinated and boosted previously, a 50µg booster dose of mRNA-1273.222 induced a superior neutralising antibody response against Omicron BA.4/BA.5 variants versus a 50µg booster dose of mRNA-1273.

For subjects with and without a Covid-19 pre-booster, the Omicron BA.4/BA.5 geometric mean titer (GMT) ratios of mRNA-1273.222 and mRNA-1273 were 5.11 and 6.29, respectively. mRNA-1273.214’s 50µg booster dose also induced a neutralising antibody response against Omicron BA.1 and Omicron BA.4/BA.5 superior to the mRNA-1273 booster, with this effect continuing through a minimum of three months.

As per data from an exploratory assessment of nearly 40 subjects, both bivalent vaccines showed strong neutralising activity against BQ.1.1, an emerging viral variant. For mRNA-1273.214 and mRNA-1273.222, the frequency of adverse reactions was found to be in line with, or less than, that of either a second or third original vaccine dose.