RIO DE JANEIRO: The Brazilian government unveiled its long-awaited national vaccination plan against COVID-19 on Saturday with an initial goal of vaccinating 51 million people, or about one-fourth of the population, in the first half of 2021.

In a document sent to the Supreme Court, which had given the government a deadline to draw up the plan, the Health Ministry said 108 million doses will be available for priority vaccination of vulnerable groups that include health workers, elderly people and indigenous communities.

The plan says 70% of the population - or about 148 million of Brazil's 212 million people - need to be immunized to stop the virus spreading. The current plan covers just about one third of that goal.

Researchers said the plan was hastily drawn up and had mistaken details about the potential vaccines.

The plan, which says each person will need two doses, does not mention a starting date for vaccination of the population nor does it detail the supplies of vaccines that it will need.

Brazil is in the midst of the world's second-deadliest coronavirus outbreak after the United States, with more than 180,000 deaths.

On Thursday, Health Minister Eduardo Pazuello pledged to vaccinate Brazil's entire population against COVID-19 next year.

The government of right-wing President Jair Bolsonaro has been under pressure from state governors and city mayors for failing to prepare in time for mass immunization or secure a diverse enough supply of vaccines.

Brazil reported 43,900 additional confirmed coronavirus cases in the past 24 hours and 686 fatalities from COVID-19, bringing total cases to 6,880,127 and the death toll to 181,123, the ministry said on Saturday.

Although Brazil has an enviable record for national vaccination campaigns and a strong public health system, Bolsonaro has repeatedly denied the gravity of the virus and is a vaccine skeptic who has said he will not take a COVID-19 shot.

He has also said his government will not buy the vaccine made by China's Sinovac Biotech Ltd that will likely be the first to complete late stage trials in Brazil. AstraZeneca , Pfizer Inc, and Johnson & Johnson's pharmaceutical subsidiary Janssen also have vaccines in Phase 3 trials in Brazil.

Microbiologist Natalia Pasternak, a critic of the government's handling of the pandemic, tweeted that there was no provision for extreme cold-storage required by Pfizer's vaccine and China's CoronVac was ignored in the plan.

Epidemiologist Ethel Maciel said that she and other scientist who were advising the government said they had not seen the plan before it was published and learned about it in the media.

Bolsonaro's government is planning to set aside 20 billion reais ($4 billion) from its budget to buy COVID-19 vaccines.

A poll by DataFolha published on Saturday showed that a growing number of Brazilians - 22% - say they are unwilling to take any COVID-19 vaccine, and most said they would not accept one made by China, as Bolsonaro's comments stoke skepticism.