The two new patients in Hai Duong were F1 of previous cases, while the patient in Ninh Thuan returned from the Philippines.
The national tally increased to 2,570, including 1,601 locally-infected cases.
A total of 2,198 COVID-19 patients have recovered, and the death toll remains at 35.
Among patients still under treatment, 37 have tested negative for SARS-CoV-2 once, 18 twice and 63 thrice.
Meanwhile, 37,878 people who had close contact with COVID-19 patients or arrived from pandemic-affected areas are under quarantine nationwide.
