30 cases were recorded in Bac Ninh, 21 in Bac Giang and one each in Dien Bien and Hai Duong.
All the cases in Bac Giang and Bac Ninh are related to existing outbreaks in the provinces' industrial parks.
The case in Dien Bien, a 33-year-old man, has made contact with a coronavirus case.
The case in Hai Duong, a 73-year-old woman, was detected via Covid-19 screening in the community.
The fourth Covid-19 wave broke out in Vietnam one month ago and so far, the nation has recorded 3,105 cases in 30 cities and provinces.
A new cluster was detected in HCMC Wednesday night but 25 positive cases linked to it have not been confirmed by the ministry.
Bac Giang continues to lead in the number of infections at 1,564, while its neighbor Bac Ninh comes second at 654. Most of the patients are workers in industrial parks.