A study by American scientists showed that a bivalent mRNA-1273.214 vaccine containing mRNA encoding the S protein derived from two variants of SARS-CoV-2: the original (Wuhan-Hu-1) and Omicron (BA.1), better protected against the present dominant variant of Omicron than the original monovalent version of the mRNA-1273 vaccine. Administration of the mRNA-1273.214 bivalent vaccine was shown to result in more than 1.5 increases of antibodies neutralizing the Omicron variant compared to those receiving the mRNA-1273 monovalent vaccine. The paper published in NEJM.
https://www.nejm.org/doi/full/10.1056/NEJMoa2208343?query=recirc_mostViewed_railB_article