All the patients, in their 20s, crossed the Ha Tien International Bordergate in Kien Giang province southern Vietnam, on April 8, and were placed in quarantine upon their arrivals.
They all tested positive the following day and were transferred to Ha Tien City Polyclinic for medical observation and treatment.
On April 9 Vietnam confirmed 15 imported cases returning from various countries abroad.
So far Vietnam has recorded a total of 2,692 coronavirus infections since the first case was detected in January 2020.
As many as 2429 patients have been discharged from hospital after making a full recovery from the disease.
Of the active cases given treatment in health facilities nationwide, 81 have tested negative at least once.
The number of deaths caused by COVID-19 and related illnesses remains at 35, including 31 in Da Nang city in central Vietnam.