On Jan. 25, 2021, Merck announced that the company had discontinued development of its SARS-CoV-2/COVID-19 vaccine candidates, V590 and V591, and planned to focus its SARS-CoV-2/COVID-19 research strategy and production capabilities on advancing two therapeutic candidates, MK-4482 and MK-7110.

This decision followed Merckﾒs review of findings from Phase 1 clinical studies for the vaccines. In these studies, both V590 and V591 were generally well tolerated, but the immune responses were inferior to those seen following natural infection and those reported for other SARS-CoV-2/COVID-19 vaccines.