Because the virus is still spreading quickly in the South American country, it is seen as an ideal testing ground for vaccine candidates.
Brazil is also helping carry out Phase 3 testing of another experimental vaccine, developed by Oxford University and pharmaceutical firm AstraZeneca.
It has a similar deal to produce that vaccine domestically if it is successful in tests, which are also being carried out in Britain and South Africa.
Brazilian health regulators announced Monday they have also authorized Phase 1, 2 and 3 trials of two more vaccines, developed by US firm Pfizer and Germany’s BioNTech.
Researchers worldwide are racing to develop and test a vaccine for the virus. There are more than 150 projects so far.
Studies published Monday in British medical journal The Lancet found two vaccine candidates were safe and produced an immune response in Phase 2 trials: the Oxford vaccine and another Chinese-made vaccine, developed by pharmaceutical firm CanSino Biologics and the Beijing Institute of Biotechnology.