China's Sinovac Biotech is starting Phase III trials of its potential coronavirus vaccine in Brazil, it said on Monday, becoming one of three companies to move into the late stages in the race to develop an inoculation against the disease.
It follows a fast-track approval for the trials by Brazilian regulators last week.
Sinovac said the study, which will be done in partnership with Brazilian vaccine producer the Instituto Butantan, would recruit nearly 9,000 healthcare professionals working in COVID-19 specialised facilities and start this month.
AstraZeneca's experimental COVID-19 vaccine, developed by researchers at the University of Oxford, and China National Pharmaceutical Group (Sinopharm) are the only other candidates in late-stage Phase III trials.
Moderna also plans to start its late-stage trial this month.
Sinovac initiated the development of the vaccine candidate in late January and is preparing a coronavirus vaccine plant, which it hopes will be ready this year and capable of making up to 100 million shots a year.
Phase I and Phase II trials typically test the safety of a drug before it enters Phase III trials that test its efficacy.
The World Health Organization (WHO) says there are 19 vaccine trials in clinical evaluation and hundreds being developed and tested around the world to stop the COVID-19 pandemic, which has killed hundreds of thousands of people and ravaged the global economy.
No COVID-19 vaccine has yet been approved for commercial use. A Massachusetts Institute of Technology analysis last year found that about one in three vaccines in the first stage of testing later gains approval.