Dr Nguyen Viet Nhung, director of the Central Lung Hospital in Hanoi, said on Monday his hospital has sought the Ministry of Health approval for a trial to find out if the Bacillus Calmette–Guérin (BCG) vaccine would mitigate the level of lung damage in Covid-19 patients.

It would also compare the symptoms vaccinated patients have with those of other groups, he said.

The vaccine has already been tested on some Covid-19 patients and people who had come into close contact with them, but the results have not studied yet.

The Ministry of Health had assigned the hospital to work with the Central Institute of Hygiene and Epidemiology to study the effects of BCG on Covid-19.

There have been studies on the vaccine’s effect on Covid-19 mortality rates, but researchers have been unable to confirm it protects from the coronavirus.

In March medRxiv, an online archive and distribution site for complete but unpublished manuscripts in the medical, clinical and related health sciences founded by Yale University in the U.S. and other stakeholders, published a preprint showing that countries which widely use TB vaccination have a lower Covid-19 mortality rate.

But it warns that preprints "should not be relied on to guide clinical practice or health-related behavior and should not be reported in news media as established information."

The study has become a prerequisite for a series of experiments around the world.

American scientists are evaluating the impact of BCG. If it proves effective, it will be tested on 4,000 health workers.

In the Netherlands, 400 frontline doctors have been vaccinated for the experiment.

A similar study has begun in Australia.

However, there have been cases of the vaccine causing complications in adults.

Nhung warned that people should not inject the vaccine at home.

"If you rely on vaccines but do not strictly implement preventive measures recommended by the Ministry of Health including wearing masks, regularly disinfecting hands, social distancing ... then there will be outbreaks with devastating outcomes."

Of Vietnam’s total of 268 Covid-19 cases, 215 have been discharged. The country has gone five days now without a new infection.