The vaccines are to arrive in phases from February, but which drug maker's product will be available first and when vaccinations can begin are still unknown.
A ban on small private gatherings that was in place in the Seoul greater area was expanded nationwide until Jan 17.
Waning was greater in older adults and those in a clinical risk group, suggesting that these individuals should be prioritized for booster doses.
Interpretation - ChAdOx1 nCoV-19 showed reduced neutralization activity against the B.
The vaccine was well-tolerated, and the independent data safety monitoring board identified no safety concerns related to the vaccine.
The extended social-distancing rules imposed on Seoul and neighbouring areas include curbs on churches, restaurants, cafes, ski resorts and other venues.