The fifteen cases recorded in Hai Duong were F1 cases that were placed into isolation earlier, thus imposing no risk of spreading the virus to the wider community.
The three cases in Quang Ninh came into close contact with COVID-19 confirmed patients, with one relating to Vietnam Poyun Electronics Co.,Ltd, the coronavirus epicenter in the locality.
The national tally is now at 2,109, with 1,480 recoveries and 35 deaths.
Among patients undergoing treatment, 33 have tested negative for the novel coronavirus at least once or several times.
Vietnam has registered 522 community cases since the recurrence of the coronavirus late last month. The virus has spread to 13 cities and provinces, with Hai Duong recording 356 cases, followed by Quang Ninh (57), HCM City (34), Hanoi (28) and Gia Lai (24).
More than 114,790 people who came from epidemic-hit regions or had close contact with COVID-19 patients are being quarantined across the nation for health observation.
In another development regarding the COVID-19 hotbed in HCM City-based Tan Son Nhat Airport, Deputy Prime Minister Vu Duc Dam has asked the local medical sector to conduct a large-scale testing in the community, particularly with all airport staff tested regularly in order to ensure the absolute safety of Tan Son Nhat Airport.