For subvariants BA 2.75.2, BQ.1.1, and XBB, in in vitro assays, bivalent boosting exceeds 1 or 2 monovalent boosting doses in neutralizing capacity.

Neutralization against BA.2.75.2, BQ.1.1, and XBB from mRNA Bivalent Booster
https://www.nejm.org/doi/full/10.1056/NEJMc2214293