Brazilian President Jair Bolsonaro never wanted to buy COVID-19 vaccines and originally bet on herd immunity beating the coronavirus, the senator leading the upper house's inquiry into the government's handling of the crisis said on Friday.

In an interview, Senator Renan Calheiros said it is too early to say if Bolsonaro had committed any criminal offense in his management of the public health crisis, and that more investigation is required.

"I think everything points in that direction," Calheiros said, regarding Bolsonaro's preference for herd immunity.

"The president first denied the disease, called it a flu, and then argued against social isolation and lockdown. Then he played down the use of masks and encouraged crowds to gather," Calheiros said.

"Why is that? Because of herd immunity, the natural immunity ... you have to encourage crowds and the spread of the virus," Calheiros added.

"This is why he never wanted a vaccine," Calheiros said of Bolsonaro, noting that the president was slow in spending billions of dollars given to him by Congress earlier in the pandemic to buy vaccines from overseas.

Herd immunity occurs when a large portion of a given population achieves immunity to a disease, sometimes through widespread infection, thereby reducing the chances of person-to-person spread.

The president's office did not immediately respond to a request for comment.

Calheiros is a veteran lawmaker and Bolsonaro critic. His report is expected to focus on the government's delays in securing vaccines, including the details of drawn-out negotiations with foreign drugmakers, and missteps in Amazonas where an infectious new variant arose.

Brazil has recorded nearly 16 million cases of COVID-19 and nearly 450,000 deaths, the second-highest death toll in the world after the United States. Bolsonaro has drawn criticism from detractors in Brazil due to his efforts to minimize the dangers of the coronavirus, shun masks and push unproven remedies.

Bolsonaro and his allies previously sought to have Calheiros removed from leading the inquiry, saying he could not be impartial because his son is the governor of Alagoas state and the inquiry would probe federal funding of state programs