Worries of a possible resurgence of COVID-19 this winter is weighing on the South Korean government, as officials mull whether it should lift the indoor mask mandate as early as January next year.

Monday’s total confirmed COVID-19 cases reached 25,667, including 63 cases from overseas, bringing the total to 27,754,149, according to the Korea Disease Control and Prevention Agency. The tally is also the highest for a Monday in more than three months since it reached 36,917 on Sept. 12.

South Korea added 30 more deaths from COVID-19 as of Monday midnight, bringing the total to 31,099. The number of critically ill patients rose to 38 from the previous day, bringing the toll to 478.

Amid woes over a virus resurgence during the winter season, Prime Minister Han Duck-soo said Friday that the government would set criteria within this month to decide whether to lift the indoor mask mandate as early as January next year or by next year March at the latest. Most pandemic-related restrictions have been lifted since May, but the mandate on masking on public transportation and indoors remains in effect.

Meanwhile, the KDCA also said it has expanded the use of updated vaccine shots to include minors aged between 12 and 17, citing waning immunity levels among the population.

The health authority pointed to how the US has made bivalent boosters available for those aged 12 and older earlier this year. It added that it decided to lower the vaccination age based on experts’ opinions that the safety of a bivalent vaccine will not be different between adults and adolescents. Most of the adverse events following vaccination were general symptoms like arm pain, it said.

Those over 12 years old who have received the first two doses of the COVID-19 vaccine, with at least 90 days since their last inoculation, are eligible for one of the two Pfizer vaccines targeting BA.4 and BA.5 variants.

Reservations and same-day vaccinations for the bivalent boosters are available for those aged 12-17 starting Monday. Those who made reservations in advance will receive their shots starting Nov. 19.

South Korea began administering COVID-19 vaccines for teenagers aged 12-17 on Oct. 18 last year and the third round of booster shots on March 14. The vaccine acceptance rate for the second jab for the age group stood at 66.5 percent, and only 11.5 percent of the teenagers got their third dose, which is far behind the second and third vaccination rates of all ages at 87.1 percent and 65.7 percent, respectively.

The health authority warned that adolescents are three to five times more prone to contracting the omicron variant, and the risk of being reinfected is about 1.8 times higher than adults.

“The COVID-19 vaccine immunity taken before wanes over time, and the bivalent boosters work better in preventing the omicron,” the KDCA said in a press release.

The KDCA also suggested adolescents with chronic lung and heart diseases, obesity and immune degradation -- those who are more prone to the virus -- receive the vaccine.

People with a history of allergic reactions to the mRNA-based COVID vaccines or who did not want to be vaccinated with mRNA can be vaccinated with Novavax, a protein-based vaccine with no genetic material.