Brazil has ordered 100 million doses of the Pfizer-BioNTech Covid-19 vaccine and another 38 million of Johnson & Johnson's, the health minister said Monday, seeking to accelerate the hard-hit country's lagging immunization campaign.

Health Minister Eduardo Pazuello said Brazil had secured a total of 563 million vaccine doses by the end of the year -- some single- and some double-dose vaccines -- and defended his handling of the pandemic, even as he confirmed that far-right President Jair Bolsonaro was looking at candidates to replace him amid a surge in new cases and deaths in Brazil.

Covid-19 has been pushing hospitals close to the breaking point across the country of 212 million people, where the death toll now stands at nearly 280,000 – second only to the United States. Bolsonaro's government has faced criticism for failing to secure enough doses of vaccine, forcing local officials to suspend immunization in some areas.

Bolsonaro, who has defied expert advice on handling the pandemic at virtually every turn -- vowing not to get vaccinated himself and joking vaccines could "turn you into an alligator" -- has recently shown signs of trying to overhaul that image. Pazuello, an army general with no prior medical experience, is Brazil's third health minister of the pandemic.

He confirmed the president was "evaluating names" to replace him. "It's true the president is thinking about a substitution," he told a news conference, vowing to ensure "continuity" and "a proper transition" if he is replaced. Earlier, Dr Ludhmila Hajjar, a cardiologist who met with Bolsonaro over the weekend, told Brazilian media she had rejected an overture from the president to take on the health minister job.

She told CNN Brasil she had since received death threats and online harassment, which she blamed on "radical" groups she said wanted to "polarize" Brazil. The South American country is deeply divided over Bolsonaro's repeated attacks on anti-pandemic measures including stay-at-home orders and face masks. Around 4.6 per cent of Brazil's population has received at least one dose of the vaccine so far.

Currently, the two shots being used in Brazil are the Oxford-AstraZeneca vaccine and the Chinese-developed CoronaVac. Pazuello presented a vaccination timeline with a somewhat improved outlook, though the doses will take time to arrive. For example, the bulk of the Pfizer vaccine doses -- 86.5 million -- will arrive in the second half of the year. The government is also negotiating another 13 million doses of fellow US pharmaceutical firm Moderna's vaccine.