COVID-19 vaccine update | China’s Sinovac Biotech vaccine is just 50% effective, say Brazil researchers

Source: Reuters

China's Sinovac Biotech, which developed the Covid-19 vaccine CoronaVac, has proved to have just 50.4 percent effective in a Brazilian trial, reported several media outlets. This is well below the initially reported efficacy rate.

Last week, the Butantan Institute had said that the efficacy rate of CoronaVac was 78 percent and claimed to offer total protection against severe cases of the disease. Brazil’s Butantan Institute, a São Paulo-based public institute that is the first to complete late-stage trials of the CoronaVac vaccine, reported CNBC.

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Despite Sinovac’s CoronaVac efficacy rate meeting the 50 percent threshold the World Health Organization approval for widespread use, Brazilian scientists and health experts have criticised state-run Butantan Institute for a lack of transparency in making public its trial data.

The Butantan Institute reportedly delayed releasing trial results three times claiming a confidential clause in its contract with Sinovac. On Tuesday, the South American country's public institute came up with the overall efficacy rate of Sinovac Biotech's CoronaVac, which is almost half of the efficacy rate of competitors like Pfizer-BioNTech and Moderna.

Sinovac Biotech's reaction:

Meanwhile, Sinovac Biotech Ltd on January 13 claimed that the low efficacy rate of 50.38 percent from its final-stage trial in Brazil is due to trial participants, mostly medical workers, who are facing a high risk of contracting with the coronavirus, reported Bloomberg.

Sinovac Chief Executive Officer Yin Weidong in his defence had said that his competitors -- Pfizer Inc. and BioNTech SE -- tested their vaccines among volunteers including people from the general population, who were less exposed to the virus compared to medical workers.

In July 2020, Weidong's firm had said its Phase III trial in Brazil would recruit nearly 9,000 health-care professionals. Later, they recruited over 13,000 volunteers and divided them between vaccinated and placebo groups. However, clarity over other participants beyond the initial 9,000 were also medical workers remains to be sceptical.

Brazil, the first country to complete a late-stage trial of the vaccine CoronaVac, has reported over 8.1 million Covid infections in total and has pinned its hopes on Chinese vaccines as wealthier countries snap up vaccines developed in the West.

Unlike Pfizer-BioNTech and Moderna, Sinovac Biotech's CoronaVac is cheaper, easier to transport, and can be stored in ordinary refrigerators.

Meanwhile, Brazil’s health regulator Anvisa has stated that it will meet on Sunday to decide if CoronaVac to be authorised for emergency use or not.

Countries approving/ordering CoronaVac:  

Apart from Brazil, Indonesia approved the vaccine for the emergency use of CoronaVac on Monday. Indonesia is the first country outside China to do so after interim data from a late-stage trial showed that CoronaVac was 65.3 percent effective. Last month, Turkish researchers had stated that their interim analysis showed the vaccine to be 91.25 percent effective, on which experts raised their doubts.