According to Ho Chi Minh City’s Center for Disease Control and Prevention (HCDC), one member of families of less than five will be tested for Covid while two are screened for bigger households.

The chosen members should be the ones posing the highest infection risk in the family, which means those that normally go out a lot and meet many people.

Everybody must be tested in areas under lockdown.

The city has rolled out a large-scale testing campaign to collect as many as five million samples, starting June 26.

Initially, it targeted finishing sample collection in 10 days. In the past week, it has carried out a testing campaign across high-risk areas, including wholesale markets and industrial zones, and around 120,000 high school students and teachers who will take part in the graduation exams this week.

As of Monday, it is unclear how many samples have been collected.

HCMC’s Vice Chairman Ngo Minh Chau told a city meeting Sunday local authorities in each district should make sure mass screenings in their localities are "organized scientifically and in order" to avoid having too many people gather at once.

Samples must be sent to laboratories three times per day at 11 a.m., 7 p.m. and before 11 p.m. instead of letting samples grow stagnant.

HCMC, home to more than 13 million including migrants, has recorded more than 6,400 cases so far in the fourth wave that hit Vietnam in late April to become the most infected locality in the nation Sunday.