As Pfizer and BioNTech begin a clinical trial of Omicron-based vaccine, the timeline to authorization is unclear.

As Pfizer and BioNTech begin clinical trial of Omicron-based vaccine, timeline to authorization is unclear – STAT

See also:

Pfizer begins testing omicron-matched COVID shots in adults – Associated Press

Pfizer and BioNTech start trials of new Omicron-specific jab – BBC

Pfizer and BioNTech begin testing an omicron-specific COVID-19 vaccine – NPR