The number of people allowed at a private gathering from Dec. 6 will be six in the Greater Seoul area and eight in other regions for four weeks.
The vaccine pass system will also be expanded to require people to show proof of vaccination vs. COVID-19 or a negative result from a diagnostic test when entering a facility.
The government on Dec. 3 announced these steps as follow-up measures for special quarantine.
Minister of Health and Welfare Kwon Deok-chul, who is concurrently first deputy director of the Central Disaster and Safety Countermeasure Headquarters, told a regular briefing that the recent surge in COVID-19 infections of over 5,000 per day and the spike in severely ill patients prompted the tougher measures.
"Cases of the Omicron variant have been confirmed in the country, and the possibility exists that it will spread further to other regions," he added.
The vaccine pass system will be expanded to 14 types of multi-use indoor facilities such as movie theaters, concert halls, private scholastic academies, study cafes, museums, libraries and internet cafes.
For restaurants and cafes, however, one unvaccinated person will be allowed within the maximum permissible range of the number of people at a private gathering given the circumstance that people have to eat. Those unvaccinated need not show their vaccine passes when going to a restaurant or cafe alone.
The new rules take effect on Dec. 6 but have a week-long grace period until Dec. 12.
To curb the spread of the coronavirus among youth, the Korea Disease Control and Prevention Agency will lower the exemption age for the vaccine pass from 18 to 11.
Minister Kwon said, "It is time to expand vaccine passes and raise vaccination rates to curb the spread of infections among youth and run schools normally such as in-person classes."
To give youth enough time to get vaccinated, they will have eight weeks or until Feb. 1 before they must start using vaccine passes.
Prime Minister Kim Boo-kyum in a statement said, "The most powerful wall of defense against COVID-19 is vaccines," stressing the importance of inoculation. "The keys to preventing a further spread are a third vaccine shot for the elderly and fully vaccinating youth."
"All companies and workplaces must thoroughly follow quarantine rules by business line and sector and reduce the risk of spreading infection by maximizing work from home until year's end."
