New Brazil data shows disappointing 50.4% efficacy for China’s CoronaVac vaccine

Sao Paulo: It's the news Indonesian President Joko Widodo probably doesn't want to hear when he lines up on Wednesday to be the first person to receive the Chinese CoronaVac vaccine kicking off a massive immunisation program.

The COVID-19 vaccine developed by China's Sinovac Biotech was just 50.4 per cent effective at preventing symptomatic infections in a Brazilian trial, researchers said on Tuesday, barely enough for regulatory approval and well below the rate announced last week.

The latest results are a major disappointment for Brazil, as the Chinese vaccine is one of two that the federal government has lined up to begin immunisation during the second wave of the world's second-deadliest COVID-19 outbreak.

Workers wearing protective gear bury the casket of a COVID-19 victim in Sao Paulo, Brazil, on Friday. The country has lost more than 200,000 people to the new coronavirus.Credit:Bloomberg

Several scientists and observers blasted the Butantan biomedical centre for releasing partial data just days ago that generated unrealistic expectations. The confusion may add to scepticism in Brazil about the Chinese vaccine, which President Jair Bolsonaro has criticised, questioning its "origins".

"We have a good vaccine. Not the best vaccine in the world. Not the ideal vaccine," said microbiologist Natalia Pasternak, criticising Butantan's triumphant tone.

Last week, the Brazilian researchers had celebrated results showing 78 per cent efficacy against "mild-to-severe" COVID-19 cases, a rate they later described as "clinical efficacy".

Urgent: Workers unload boxes of the Sinovac coronavirus vaccine CoronaVac in Jakarta, Indonesia, last week.Credit:Bloomberg

Joko will be given a CoronaVac shot on Wednesday, his office said, in a sign of the priority placed on immunisation in a country that has done far less than its South-east Asian neighbours to track and contain the virus.

Minister of Health Budi Gunadi Sadikin told parliament on Tuesday that nearly 1.5 million medical workers would be inoculated by February, followed by public servants and the general population within 15 months.

Indonesia on Tuesday reported a daily record 302 coronavirus deaths, taking fatalities to 24,645. Its infections are at their peak, averaging more than 9000 a day, with 846,765 total cases.

Palacios and officials in the Sao Paulo state government, which funds Butantan, emphasised the good news that none of the volunteers inoculated with CoronaVac had to be hospitalised with COVID-19 symptoms.

Public health experts said that alone will be a relief for Brazilian hospitals that are buckling under the strain of surging case loads. However, it will take longer to curb the pandemic with a vaccine that allows so many mild cases.

"It's a vaccine that will start the process of overcoming the pandemic," Pasternak said.

Researchers at Butantan delayed announcement of their results three times, blaming a confidentiality clause in a contract with Sinovac.

In the meantime, Turkish researchers said last month that CoronaVac was 91.25 per cent effective based on an interim analysis.

Butantan officials said the design of the Brazilian study, focusing on frontline health workers during a severe outbreak in Brazil and including elderly volunteers, made it impossible to compare the results directly with other trials or vaccines.

Still, COVID-19 vaccines in use from Pfizer with partner BioNTech and Moderna proved to be about 95 per cent effective in preventing illness in their pivotal late-state trials.

The disappointing CoronaVac data is the latest setback for vaccination efforts in Brazil, where more than 200,000 people have died since the outbreak began – the worst death toll outside the United States.

Brazil's national immunisation program currently relies on CoronaVac and the vaccine developed by Oxford University and AstraZeneca – neither of which has received regulatory approval in Brazil.

Anvisa, which has stipulated an efficacy rate of at least 50 per cent for vaccines in the pandemic, has already pressed Butantan for more details of its study, after it filed for emergency use authorisation on Friday.

The regulator said it will meet on Sunday to decide on emergency use requests for CoronaVac and the British vaccine.

AstraZeneca failed to deliver active ingredients to Brazil over the weekend, leaving the government scrambling to import finished doses of the vaccine from India to begin inoculations.


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