Speaking at a government meeting on Covid prevention on Monday, he pointed to the high risk of a new outbreak in Vietnam and called on related ministries and other agencies to control borders and the immigration process.

Local governments need to persuade the public to wear masks at large gatherings, he said. Vietnamese people have been advised to avoid large gatherings as a Covid prevention measure, but explicit bans are only imposed in time of outbreaks.

Vietnam has secured around a million doses of vaccines made by British-Swedish firm AstraZeneca, either through contracts or global vaccine access mechanism Covax.

It has so far vaccinated around 260,000 people, mainly frontline workers.

It is also developing four Covid-19 vaccines that are in various stages of testing.

Nanogen recently finished the second phase of human trials of its Nanocovax, which has proved to be immunogenic in all volunteers.

The third phase is expected to begin on May 5.

Covivac by the Institute of Vaccines and Medical Biologicals is expected to finish its first phase of human trials on May 15 and begin the second in June.

The Health Ministry last month said local firms were in talks with companies in the U.S. and India for diversification of vaccine sources as Vietnam seeks to obtain a total 150 million doses this year to immunize 70 percent of its population.