Four months into a Covid-19 vaccination campaign marred by shortages and delays, hard-hit Brazil is still struggling to find enough doses, as political and diplomatic blunders prolong its pandemic nightmare.

Around 33 million people - 15% of the population - have received at least one vaccine dose in Brazil, a proportion still too small to have a substantial impact on the virus' spread.

Targeted by a senate inquiry over its handling of the pandemic, President Jair Bolsonaro's government is facing criticism for failing to secure more vaccines, including its refusal of offers to purchase millions of doses and diplomatic tension with China that may be slowing the import of vaccine ingredients.

"We don't have enough doses right now to vaccinate as fast as we should," said Margareth Dalcolmo, a pulmonologist and researcher at leading public health institute Fiocruz.

"We ought to be vaccinating younger people already, especially given that younger demographic groups are currently driving transmission," she told AFP.

But first, Brazil still has to vaccinate 80 million people from high-priority groups, including the elderly, indigenous people and health workers.

Vaccine doses meanwhile continue to arrive in a trickle, although the government maintains it will be able to vaccinate all adults by the end of the year.

Brazil has lost more lives to Covid-19 than any country except the United States - more than 430,000 - and has one of the highest death tolls per capita in the world.

Though the current wave has eased somewhat since April, the virus is still killing a staggeringly high number of people in the country, nearly 2,000 a day.

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Despite its huge size, the South American country is known for executing turbo-charged vaccination campaigns.

In 2010, Brazil vaccinated more than 80 million people against H1N1 - the swine flu virus - in less than three months.

"We've gotten better since the start of the year, but we're still a long way from where we need to be," said Joao Viola, president of the Brazilian Immunological Society's scientific committee.

Brazil started out using two vaccines, Oxford/AstraZeneca's and Chinese-developed CoronaVac, both of which it has licenses to produce locally.

The drive got a boost last month with the arrival of the Pfizer vaccine. But only about two million of the 100m doses Brazil has ordered have been delivered so far.

All three shots require two doses.

Brazil could have secured more Pfizer doses faster, but Bolsonaro's government refused an offer last August to purchase more than 70m of them.

The far-right president, who has persistently snubbed expert advice on handling the pandemic, joked that the vaccine could "turn you into an alligator" - only to change course months later and allow a deal with the US pharmaceutical giant.

"Worldwide demand for vaccines is very high, so those who were slow to sign deals are receiving their orders later," said Mr Viola.

Indonesia pauses distribution of a batch of AstraZeneca vaccine

Indonesia has suspended distribution of a batch of the AstraZeneca vaccine to run tests for sterility and toxicity following the death of a 22-year-old man a day afte rimmunisation, the health ministry said.

The 'CTMAV547' batch consists of 448,480 vaccine doses that arrived in the southeast Asian nation last month - part of a delivery of more than 3.85 million doses from the Covax Facility, backed by the World Health Organization.

Some of the doses have been distributed in the capital city Jakarta and the province of North Sulawesi, as well as given to the military, the ministry said in a statement.

A national committee in charge of monitoring effects of coronavirus vaccination launched an investigation earlier this month after a 22-year-old man in Jakarta died a day after receiving an AstraZeneca shot.

The man received his dose from the CTMAV547 batch, a health ministry spokeswoman told Reuters.

"This is a form of caution by the government to ensure the safety of this vaccine," she said in a statement, adding that distribution of other batches of AstraZeneca vaccines will not be affected.

The batch test could take at least two weeks, said the head of the vaccine monitoring committee.