South Korea on Tuesday confirmed three more cases of so-called breakthrough COVID-19 infections, bringing the total caseload here to four.

The Korea Disease Control and Prevention Agency (KDCA) said the four people have tested positive for the novel coronavirus even after receiving two doses of a vaccine.  

A "breakthrough case" is when a person tests positive form COVID-19 between their first and second doses of a two-dose regimen or a person tests positive after full vaccination.

Of the four people, two were exposed to the virus before a two-week period after the full vaccination ended, while two others were infected after the two-week period.

The KDCA said similar cases will increase as the country's vaccine rollout revs up, adding that those who are fully inoculated still need to wear facial masks.

The authorities said even after the full vaccinations, a person can be infected with COVID-19. They also said that those who are classified as breakthrough infection cases have mild symptoms or are asymptomatic.

As of Tuesday, 1.85 million people, or 3.6 percent of the country's population, have been fully vaccinated after receiving both doses of two-part vaccines, the KDCA said. (Yonhap)