South Korean political and health leaders are standing firm on their goal of getting to COVID-19 herd immunity in November, which has been marked as a point of return to normalcy, after reaching a vaccination threshold of 70 percent of the population.

So far the term herd immunity has been loosely thrown around by those in political circles and public health offices alike. But the concept has been largely understood as some degree of a return to normal life and retirement from the excruciating practice of social distancing.

President Moon Jae-in said back in June that a “maskless Chuseok” will be possible as vaccinations progress, and top officials at the Ministry of Health and Welfare and the Korea Disease Control and Prevention Agency have repeatedly associated having herd immunity with restoration of normal life.

What herd immunity would look like when Korea gets there in November has been more concretely laid out for the first time during Health Ministry’s closed-door briefing Thursday.

Health Ministry spokesperson Son Young-rae told reporters that even after herd immunity is reached in November, face masks and other safety steps will remain necessary.

Asked how the administration was defining herd immunity, Son said it was “when transmissions slow and fatality rates fall as large proportions of Koreans are immunized against COVID-19.” “The day-to-day operations of the society will be significantly close to normal,” he said. “But that doesn’t mean we can do away with face masks or other basic health protocols.”

Herd immunity is “thought to be a situation where risks are controlled through continued compliance with basic health protocols,” he said.

Son said in the same briefing 70 percent of Korea’s roughly 51 million people will complete their vaccinations between late October and early November, adding on to Moon’s reaffirmation of the administration’s vaccine goal on Monday.

Moon told a meeting of senior presidential secretaries and aides earlier this week that 36 million Koreans will be vaccinated with at least one dose of a vaccine before Chuseok, a national holiday falling Sept 18-22.

Since Pfizer and Moderna vaccines -- which are administered over a minimum interval of four weeks per the guidance updated July 23 -- are to be mainly available from August onwards, the finishing point of second-round vaccinations for 70 percent of the population is anticipated to be around a month after Chuseok.

But Son gave a more conservative estimate, saying, “The majority of Koreans will become fully vaccinated by the end of October or the start of November. By September’s end is when at least 70 percent will have gotten one dose.”

What the Health Ministry has described as herd immunity Thursday far is from how the term has been previously communicated to the public, or how it is commonly understood as a public health term, according to experts. 

“The notion of herd immunity has grown rather elusive with COVID-19, but I wouldn’t call that herd immunity,” said Dr. Paik Soon-young, emeritus professor at Catholic University of Korea’s department of microbiology.

“But what is more important is that even without herd immunity, the pandemic is expected to become substantially more manageable as more people get vaccinated, with reductions in deaths and hospitalizations,” he added.

“Generally speaking, herd immunity is when the spread of a virus can be contained without non-pharmaceutical interventions such as social distancing, masking and hand washing, after a large chunk of population in a given community becomes immune either through infection or vaccination,” said infectious disease professor Dr. Kim Woo-joo of Korea University.

Kim went on, “We also need to keep in mind that 70 percent vaccination rate does not necessarily translate to corresponding rates of neutralizing antibody responses across the vaccinated population.” “Plus, there is a question of immunity waning over time,” he said.

While the key task facing Korea remains delivering first doses to people who have never been vaccinated, older, immunocompromised people who were given vaccinations months ago are now getting what is known as “breakthrough infections,” he said. In recent weeks, outbreaks among the vaccinated have been reported at nursing homes, whose residents were first in line for a vaccine when the national campaign kicked off in February. 

Korea has no plan to give a third booster shot to vulnerable people first vaccinated in February and March.

Dr. Eom Joong-sik, infectious disease specialist at Gachon University Medical Center, also said, “Herd immunity as I understand it is when infections remain at a stable level in the absence of social distancing.”

He pointed out that in light of highly contagious new variants, Korea needed a vaccination rate greater than the initially aimed 70 percent. “Delta raises the bar higher -- now the vaccination target should be 80 percent, or even 90 percent,” he said. “That is, if delta continues to be the dominant strain. We could be fighting against a new, different variant then.”

Children under 18 years of age, who make up 15 percent of the population, are currently left out of vaccine plan, which also complicated the equation, Eom said.

Out of the 51 million people in Korea, 39 percent had received at least one dose of a vaccine by Wednesday’s end, while 14 percent were fully vaccinated. Over the month of July, an average of around 90,000 doses were administered per day.

By Kim Arin (arin@heraldcorp.com)