As a tertiary center with 2,500 beds, Linton's hospital only has a few COVID-19 patients, who have been transferred from elsewhere in the country. But he said strict screening and prevention measures have been taken, including three safety clinics set up to screen people before they enter the main building.

If people have symptoms, or COVID-19 contact history, they will be sent to the testing center, he said. "The system is upgraded all the time. Many doors are locked in the hospital and only a few entrances are being used."

South Korea made early preparations to control and prevent COVID-19, and having the laws in place allowed the country to be quick and decisive when rolling out various measures, said Jerome Kim, director-general of the International Vaccine Institute.

The IVI is a non-profit organization based in Seoul, and established in 1997 at the initiative of the United Nations Development Programme.

Kim said the core of South Korea's success lies in the country's approach to test, isolate, track and treat people who are infected and who might be exposed to the virus.

"South Korea has a very vibrant biotech community and that's one of the reasons the testing was up-and-running so quickly," Kim said.

"The same thing applies in vaccines. Vaccines are a bit harder because it takes a bit longer to develop them ... but currently both large and small companies are involved in vaccine development in South Korea."

Linton said, "We are still worried about cluster infections," adding that such concerns are not just directed toward the Shincheonji religious group, but are aimed more at other churches that are refusing to cooperate or have their members go into self-isolation.

While the majority of churches have closed or are holding services on the internet, Linton said that about 10 percent of them are still conducting physical services.