Poor decision-making was behind the failure to vaccinate the 301-strong crew on an anti-piracy ship before they left for Africa, Defense Minister Suh Wook said as he apologized Tuesday for a huge COVID outbreak aboard the 4,400-ton destroyer Munmu the Great.

Suh was facing criticism over the outbreak that forced the military to cut short its overseas mission for the first time. The military said the seamen could not get COVID shots because they had little expertise in handling a possible allergic reaction to the vaccine or the ability to manage its extreme storage conditions.

“There had been some oversight. And I feel responsible for the massive outbreak. We will look at all our missions overseas and make sure we do not repeat the same mistake,” Suh said, adding that the ministry will fully assist members of the Cheonghae Unit, who arrived here late Tuesday.

The military was found to have ignored the ministry guidelines in December, when they advised priority units that need vaccination, including warships on overseas mission, to carry COVID antigen tests.

Instead, the Cheonghae Unit, which headed to Africa ahead of the March vaccination campaign, decided to pack COVID antibody tests, which health experts say do not provide a reliable method to immediately respond to an outbreak because antibodies take weeks to develop.

“The accuracy of the antigen tests was also debatable at the time, so we leaned on antibody tests, which were FDA-approved,” a senior military official said.

The crew, who were airlifted to Seoul Air Base, went through COVID tests again upon landing. The initial test taken aboard the ship showed 247 tested positive for COVID-19, including the commander and deputy commander. Fifty were negative with four undecided, and twelve were in critical condition.

The twelve who were moderately ill were sent to hospitals, along with some of those who tested positive with the new tests. Those who were negative were sent to COVID treatment centers.

Meanwhile, a fully vaccinated 148-strong Navy contingent took over the 4,400-ton warship and is sailing it back home, a journey that should take at least 40 days. A second destroyer reportedly reached the Gulf of Aden to replace the vessel as part of six-month rotational deployment, which was to follow in August.

The outbreak on the warship is believed to have started on July 2, a day after the destroyer left a nearby port where it had made a four-day supply stop. A seaman exhibited cold symptoms. He was treated with cold medicine but was not tested for the coronavirus.

On July 15, six patients tested positive for the coronavirus. Many crew members exhibited cold or pneumonia symptoms. The military then tested every service member aboard with help from Korean diplomatic missions nearby.

About 72 percent of some 1,300 South Korean soldiers deployed overseas have received their COVID shots, according to the military. All four overseas missions have received vaccinations with help from either the UN or the local authorities, except for the Cheonghae Unit.