"Now is not the time to relax," he said at a government meeting.
The Health Ministry confirmed zero new Covid-19 cases Tuesday evening, keeping the nation’s tally at 270 for four days straight.
For now, the number of active Covid-19 patients in the country remains at 48, including eight relapses.
Deputy Health Minister Nguyen Thanh Long said earlier Tuesday that studies of new coronavirus samples taken from the five relapsed patients reveal that the virus in their bodies now are "inactive."
Long said the virus was cultivated but did not multiply.
"Theoretically, the chance that these patients can infect others is very low," Long said.
Of the active cases, eight have tested negative once and seven twice.
Addressing a government meeting Tuesday afternoon, PM Phuc said Vietnam has basically managed to contain Covid-19.
But the nation cannot afford to relax its vigilance yet, he said.
The PM has allowed localities to restore production and business, but several "non-essential" services like bars, karaoke parlors, massage parlors, beauty clinics and entertainment facilities are to remain closed until further notice.
In a directive issued last Saturday following social distancing relaxations, he also asked localities to stop all religious gatherings, sports events and crowded festivals in public places, as also other "unnecessary" events.
By last Friday morning, Vietnam had gone eight straight days without reporting any new infections. Then, that evening, there were two new cases confirmed, both Vietnamese students returning from Japan, taking the nation’s count to 270.
Of the total, 222 patients have been discharged from hospitals.
The Covid-19 pandemic has reached 210 countries and territories with a reported death toll of around 212,300.