Health authorities will set a six-month valid period on COVID-19 entry passes, considering the waning effect of vaccines over time.

Adults aged 18 to 49 will also get booster shots five months after their last inoculation.

These are a couple of the updated antivirus measures announced on Monday following a special virus response meeting. The country has been reporting a huge uptick in infections as well as critical cases since the transition to normal life began on November 1.

Under a new rule set to take effect from December 20, adults will need to get boosters after a five-month interval in order to keep their entry passes valid.

For the 18 to 49 age group, reservations for third shots will open on Thursday for jabs that will start on Saturday. Signups for same-day leftover vaccines will also start on Thursday.

The entry pass system currently requires people to show proof of vaccination or a negative test result before entering "high-risk" establishments such as bars and gyms.