The Chinese developer of CoronaVac has said preliminary results of trials of the potential vaccine against the Covid-19 virus indicate that it is safe and triggers immune responses in older people, Reuters reports.

The news agency quotes Liu Peicheng, a spokesman for the developer, Sinovac Biotech Ltd, as saying in writing that CoronaVac caused no severe side effects during the first two phases of the trials, when it was tried out on 421 people at least 60 years old.

Over 90 percent of those given two shots of CoronaVac showed significant increases in their antibody levels, Reuters quotes Mr Liu as saying.

In July the Brazilian state-run news agency, Agência Brasil, reported that the last stage of trials of CoronaVac on humans had begun in Brazil, where it was due to be tried out on about 9,000 people in various parts of the country.