An infectious disease expert says that while the vaccine rollout is in full swing in South Korea, reaching herd immunity may be a tall order.

Seoul National University professor Oh Myoung-don, who heads the country's central clinical committee on new infectious diseases, said at a press conference on Monday that COVID-19 is likely here to stay.

While herd immunity is believed to be attained when 70 percent of the population is vaccinated, Oh said that is not the case, noting there isn't a vaccine yet that is over 95 percent effective in preventing secondary transmissions.

The professor said the Pfizer vaccine's 95 percent efficacy refers to the prevention of contracting the virus and not the prevention of the spread.  

Oh said that even if herd immunity is achieved, high-risk groups must continue precautions as the duration of immunity has not been clearly confirmed. Given such various factors, the professor is doubtful about reaching herd immunity or eradicating COVID-19.

He said the virus can become like the flu that is always with us, and added the vaccination program should focus more on protecting the elderly and high-risk people and minimizing the damage rather than rooting out the virus entirely.