Health authorities have stated that achieving herd immunity against COVID-19 is, in theory, difficult to accomplish because variants continue to emerge and antibody levels will decrease as time passes.

In an online briefing on Thursday, Kim Byung-guk, an official from the Central Disease Control Headquarters, said that even if over 90 percent of the public have developed antibodies through vaccination or natural infection, it is difficult to say that that the population has attained herd immunity as variants continue to emerge.

Authorities on Tuesday announced the results of a sample survey of some 16-hundred people that showed antibody levels stood at nearly 95 percent of all residents.

Kim said that with new variants continuously mutating, the antibody rate alone does not indicate herd immunity.

The nationwide survey was conducted from January to April. A much larger study involving ten-thousand participants per quarter will be carried out from July.