South Korean health authorities say high-risk groups such as nursing home residents will need to receive a booster shot for COVID-19. 

Korea Disease Control and Prevention Agency(KDCA) Commissioner Jeong Eun-kyeong said in a media briefing on Monday that dates for a third shot for high-risk groups at nursing homes is to be determined and will be decided based on surveying the presence of antibodies following second shot inoculations. 

The determination comes after a series of breakthrough cases were reported in senior groups, including 41 cases linked to a nursing home in Gijang County in Busan. That figure represents nearly 18 percent of the home's residents and staff members. 

Noting that underlying symptoms of nursing home residents, as well as the close living space they reside in, make them prone to breakthrough infections, the KDCA chief said the government will also strengthen quarantine measures in such facilities.