'On June 28, 2022, researchers from Pfizer–BioNTech and Moderna presented data on their bivalent vaccines to the FDA’s Vaccines and Related Biological Products Advisory Committee (of which I am a member). The results were underwhelming. Bivalent boosters resulted in levels of neutralizing antibodies against BA.1 that were only 1.5 to 1.75 times as high as those achieved with monovalent boosters.'
https://www.nejm.org/doi/full/10.1056/NEJMp2215780