A fully vaccinated Navy officer has tested positive for the new coronavirus, marking the first breakthrough infection reported in the military, officials said Thursday.

The officer, based in the southeastern city of Busan, was confirmed to have contracted COVID-19 after developing symptoms despite having received two doses of AstraZeneca's vaccine in April and early June, according to the officials.

A breakthrough case refers to when a person is diagnosed with the virus two weeks after being administered with the full-dose regimen.

Health authorities earlier said South Korea has confirmed 44 such cases as of last Thursday.

Separately, a soldier based in the northeastern border county of Hwacheon was found to be infected while away from his base on a vacation before discharge, while an Army civilian official in the central county of Yeongdong was confirmed to be infected after coming into contact with an individual who tested positive earlier, according to the defense ministry.

The latest cases raised the total number of infections reported among the military population to 1,025.

Nationwide, South Korea added 762 new cases Thursday, bringing the total caseload to 157,723.

With the greater Seoul area facing a potential resurgence in new infections, the ministry said the military will extend the current social distancing rules in barracks for another week. (Yonhap)