Bac Giang province, which about 40km away from Hanoi capital, recorded 45 cases in quarantine and lockdown areas closely tied to outbreaks at industrial parks in the locality.
Elsewhere, nine cases were documented in Bac Ninh, another COVID-19 hotspot, and one case in Long An.
Vietnam has confirmed 3,892 local infections in 34 cities and provinces nationwide since the virus recurred in late April.
Bac Giang was the worst hit locality, registering more than 2,100 cases.
Also the same day, 54 COVID-19 patients were discharged from hospital following making a full recovery from the disease.