Patients "1146-1148" are a 46-year-old man, a 35-year-old woman and a 36-year-old man who arrived October 20 at the Van Don Airport in the northern province of Quang Ninh on Vietnam Airlines flight VN8.
They were quarantined upon entry before being confirmed positive for the novel coronavirus on October 22.
"Patient 1146" is being treated at the Bac Ninh General Hospital in the northern eponymous province, while the other two are undergoing treatment at the National Hospital for Tropical Diseases in Hanoi.
Health authorities also announced Thursday the recovery of three Covid-19 patients, all Indian experts, treated in the Mekong Delta province of Dong Thap.
Of the 61 active cases, 23 have tested negative for the virus at least once.
Vietnam has gone 50 days without any community transmission. Around 14,000 are in quarantine.
Of the national Covid-19 tally of 1,148, 35 have died. Many of the deaths were of elderly patients with underlying conditions like diabetes and kidney failure.e 35 died from the disease. Many of the fatalities are elderly patients with underlying conditions like diabetes and kidney failure.