Yes, you need to show that the new vaccine works against the new variant but not that it’s safe. So it will be much faster
Anyway, how do they know the usual but new seasonal flu vaccine is safe ? Can't the same framework apply ?
https://www.cdc.gov/flu/vaccines-work/effectivenessqa.htm
Manufacturers guess which flu strain will predominate and start working 9-12 months early to capture the data for approval.
There is no way a new Covid mRNA vaccine will be approved with safety and efficacy data from a clinical trial. That will be take months to complete.
You meant 'without', right?