The government said Friday that it was not considering additional quarantine measures even after confirming the first case of BA.2.75, dubbed "Centaurus," the most contagious Omicron subvariant with greater immune-avoiding properties than BA.5.

On Thursday, Korea confirmed the first BA.2.75 case from a 60-year-old man living in Incheon, west of Seoul, with no overseas travel history.

"There is a possibility that the BA.2.75 mutation will spread around the local communities," said Son Young-rae, head of the social strategy team at the Central Disaster Management Headquarters. "We will monitor whether BA.2.75 will become a dominant strain in Korea, but do not think there is a need to change the countermeasures right now."

If BA. 2.75's share among the total caseload increases, the government will comprehensively review the situation, considering its transmission power, fatality, and the degree of severity in other countries, he added.

Son also stressed that the government is not considering immigration control in response to the increase in overseas inflows.

"To block Covid-19 variants’ entry, the government is supposed to reinforce strong quarantine measures at airports," Son said. "However, such a move’s effect is not great, and the social and economic damage caused by the influx of variants from overseas is not that so significant, either."

Son cited that after the Omicron outbreak, the overall fatality and severity rates have dropped, variants with strong propagation power are appearing, and countries are actively using vaccinations and treatments to reduce the fatality rate as much as possible.

"However, if Korea confirms that an unusual type of variant, which has a significant increase in the fatality and severity rate, emerges as a dominant strain, the government will actively review strengthening entry measures," the official emphasized.

Meanwhile, the government pledged to strengthen disinfection efforts at airports and major tourist destinations by mobilizing nearly 2,600 workers. It then advised inbound travelers to receive the polymerase chain reaction (PCR) test on arrival rather than within three days and to stay home until their test results are available.

Officials stressed that they would create an environment where people can travel confidently during the holiday season and positively respond to surging demands here and abroad.

Korea's daily Covid-19 tally also maintained a "weekly doubling phenomenon" to nearly 40,000 on Friday.

The nation added 38,882 Covid-19 infections on Thursday, bringing the total caseload to 18,641,278, the Korea Disease Control and Prevention Agency said.

Health officials expect the spread of the virus will continue for the time being as the R0, an estimated reproductive rate of how many people may contract the virus from one infected person has stayed above 1 for the second consecutive week.

However, quarantine officials said they judged the situation still under control as the increase in the number of deaths and critically ill patients in hospitals is small. In contrast, the hospital bed capacity remains largely available.

"Since Omicron became the dominant strain, the fatality rate has been lower than before," Son said. "While the cumulative fatality rate for the past two years was 0.13 percent, when looking at May alone, it was 0.07 percent."

Considering that the fatality rate of seasonal flu is usually evaluated at 0.05 to 0.1 percent, he added that the fatality rate of Covid-19 after Omicron is close to the level similar to that of seasonal flu.

In response to the resurgence, the government has also expanded eligibility for second booster shots to all people 50 and older, including those 18 and older with underlying health conditions. It will start administering them next week.

As of Thursday, 44.63 million, or 87 percent of the population, had completed the full two-dose vaccinations, and 33.4 million, or 65.2 percent, had received their first booster shots.

About 4.61 million people, or 8.7 percent of the population, had gotten their second booster shots, according to the KDCA.