Of them, three are men aged 21-34 in northern Hai Duong Province, the Covid-19 epicenter ever since infections returned to Vietnam's community on January 28.
The other patient is also a man, 50, in the Central Highlands province of Gia Lai. His infection was detected following a mass testing after community transmissions spread widely in the Central Highlands province during the past week.
With them added to the list, Vietnam has registered 402 domestic cases since January 28 and infections have so far spread to 12 cities and provinces, including 293 in Hai Duong and 47 in its neighbor Quang Ninh.
Vietnam has by far reported 1,985 cases and 517 of them are active.