South Korea's new COVID-19 cases fell below 40,000 on Thursday, breaking an upward trend that had continued for the past two days.

The country reported 34,987 new COVID-19 infections, including 55 from overseas, bringing the total caseload to 25,431,105, the Korea Disease Control and Prevention Agency said.

Thursday's tally is a 5,855 drop from the previous day, but slightly higher than the past seven day average, KDCA data showed.

The country reported 26 deaths, bringing the death toll to 29,069.

The number of critically ill patients came to 242.

Health authorities said Wednesday it will expand booster shot vaccinations to all adults aged over 18, as the country braces for a possible "twindemic" outbreak of COVID-19 and the seasonal influenza this winter.

Starting Thursday, reservations for COVID-19 boosters will open for adults aged from 18 to 59.

Individuals can choose between three types of mRNA vaccines -- Moderna and Pfizer shots against the BA.1 variant, and Pfizer shots against the BA.4 and BA.5 variant -- or protein-based vaccines such as Novavax and Skycovione.

Those who have either tested positive for COVID-19 or completed two full rounds of inoculations more than four months ago, are eligible for booster shots, the KDCA said. (Yonhap)