Health authorities have called for all high-risk groups to be vaccinated against COVID-19 with a winter resurgence of the virus seemingly inevitable.

Jung Ki-suck, the head of the government's advisory panel on infectious diseases, said on Monday that based on past winter pandemic trends, another wave of the virus will occur in December even without a new variant.

He explained that the consistent spike in winter derives from the season's prevalence of viruses and the relative decrease in viral immunity. Whether the new mutations will be the dominant strains will likely be determined in December.

Jung appealed strongly to those at high risk, especially people over 60 years old, to get inoculated, asking local governments to actively encourage vaccinations.