The cases, 12 imported and eight domestic, are all Vietnamese.
This brings the national count to 2,962, with 1,595 domestically-infected cases.
A total of 40,563 people who had close contact with COVID-19 patients or arrived from pandemic-hit areas are being quarantined nationwide.
Meanwhile, 2,549 patients have been given the all-clear, and the death toll remains at 35.
Among the patients under treatment, 19 have tested negative for the coronavirus once, 19 twice and 34 thrice.
After locally-infected cases were detected in late April, localities around the country are tightening epidemic prevention measures.
