"Patients 1114-1122," all males aged 27-41, landed October 6 at the Tan Son Nhat International Airport in Ho Chi Minh City on Indigo Airlines flight 6E9471.
They were quarantined in the southern province of Dong Thap and have tested positive for the novel coronavirus twice. They are being treated at the Sa Dec General Hospital.
Another seven passengers on the same flight had tested positive earlier.
Of Vietnam's 1,122 Covid-19 cases, 1,029 have recovered, three of them on Wednesday. The death toll stays at 35.
Among the active patients, 26 have tested negative at least once. All the patients are in stable health.
More than 12,000 people are in quarantine nationwide. Covid-19 has claimed over one million lives globally.