The 68-year-old woman and the 55-year-old man, tagged patients "1123 and 1124," landed October 11 at Quang Ninh Province’s Van Don Airport on Vietnam Airlines flight VN0001 flight.
They were quarantined on arrival at a facility in the northern province of Hung Yen, where they tested positive for the novel coronavirus two days later.
The two patients are being treated at Hanoi’s National Hospital for Tropical Diseases.
Also Thursday, a 48-year-old Indian man was announced Covid-19 free in Hanoi.
Among the currently active 56 cases, 25 have tested negative at least once. Around 13,000 are in quarantine nationally.
Of the 35 Covid-19 fatalities recorded in Vietnam so far, many were elderly patients with underlying conditions like diabetes and kidney failure.
Vietnam has recorded no community transmission of the virus for over a month.