A fourth wave began in late April starting with several people who tested positive after finishing two weeks of quarantine. They had breached the self quarantine protocol, which required them to isolate themselves at home for two weeks after completing quarantine.

"Vietnam might consider using technology to make sure people are physically in their homes in mandatory quarantine after completing a 14-day period at centers," Dr. Karen Grépin of the University of Hong Kong said.

That is used in Hong Kong where authorities require people to wear a wristband while self-isolating for two weeks, she said. The band pairs with a phone app and is designed to detect if a person has left their hotel room or house.

Grépin warned that there is some evidence the virus is actually being transmitted within quarantine facilities, and to reduce the transmission risks she suggested authorities should put people from lower-risk countries and places where cases are not severe in a separate area.

"Ones coming from higher-risk countries should stay in the more secure facilities."

A quarantine center in Cu Chi District, HCMC in March 2020.
Photo by VnExpress/Quynh Tran. 

A quarantine center in Cu Chi District, HCMC in March 2020. Photo by VnExpress/Quynh Tran.

If quarantined in hotels, she said people who arrive at similar times must be roomed near each other and away from newer arrivals, a system that could help minimize possible transmission, she said.

Staff working in such hotels and people interacting with quarantined people, including health workers, need to be vaccinated as far as possible, she said.

Professor Mark Jit, London School of Hygiene and Tropical Medicine, the U.K., said people should be regularly tested during quarantine so that if they are infected it would be detected quickly.

There are different algorithms that Vietnam may examine for testing. For most countries, it's been shown that 10-day quarantine with two tests could be enough to help reduce the transmission risk, and 14 days are enough in most cases, helping reduce imported infections by 99.9 percent, Jit said.

On May 5 Vietnam increased the mandatory quarantine period from 14 to 21 days for both foreign arrivals and those who come into contact with Covid patients.

Jit said the chance of someone still being infectious after 21 days "is really very low."

Grépin corroborated this, saying the vast majority of the risk is already reduced with a 14-day quarantine, and scientists do not have much evidence that it has a public health benefit beyond 14 days.

Dr Ali Mokdad of the University of Washington, the U.S., said even with the Indian variant, quarantining for 14 days is more than enough because the maximum incubation period of the virus is 14 days.

He said quarantining should be done correctly along with tests, and warned that with a 21-day quarantine the chance of people cheating would increase since they have the need to meet family and friends.

"Every country has the right to decide. But scientifically 14 days are enough."

Albert Icksang Ko of the Yale School of Public Health, the U.S, said the large majority of people stop shedding infectious viruses before 14 days, and there might be little added value in extending to 21 days.

Dr Hiroyuki Moriuchi, Nagasaki University Hospital, Japan, said Vietnamese authorities should have measures to ensure people completing their quarantine regularly report any health problem, so that the country could timely stop the transmission.

In order to find out undiagnosed patients, comprehensive transmission survey should be conducted, he said.

Experts said besides quarantining, Vietnam also needs to increase testing to detect variants and decide what measures are required.

Professor Kelley Lee, Simon Fraser University, Canada, said genomic sequencing is critical to ensuring that variants are identified before reaching the wider community.

She suggested performing whole genome sequencing (WGS) on some samples that test negative as well because some variants are eluding detection with some tests without WGS and so sequencing a negative sample would increase the chances of identifying variants.

Some random testing could be done in the community to identify asymptomatic cases, and this must be risk-based, she added.