South Korea may shorten the period between the booster jab and the final round of inoculations.
Currently, South Korea recommends people 50 and over get boosters at least six months after being fully vaccinated.
Those in nursing homes or working at high-risk facilities can get their booster as early as five months after.
But Seoul's health minister says health authorities are currently reviewing the timeline for booster jabs meaning extra shots given three to four months after final doses.
The nation has been seeing a rising number of critical cases among the elderly and breakthrough cases.