On Jul. 27, 2022, Pfizer and BioNTech announced that the companies had initiated a randomized, active-controlled, observer-blind, Phase 2 study to evaluate the safety, tolerability, and immune response of an enhanced COVID-19 mRNA-based vaccine candidate at a 30 ﾵg dose level. This next-generation bivalent COVID-19 vaccine candidate, BNT162b5, consists of RNAs encoding enhanced prefusion spike proteins for the SARS-CoV-2 ancestral strain (wild-type) and an Omicron variant. The enhanced spike protein encoded from the mRNAs in BNT162b5 has been modified with the aim of increasing the magnitude and breadth of the immune response that could better protect against COVID-19.