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

Last week, the Brazil's 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.

January 13, 2021 / 05:13 PM IST
Source: Reuters

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.

Indonesia starts mass COVID-19 vaccinations with president Joko Widodo

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.

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COVID-19 Vaccine

Frequently Asked Questions

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How does a vaccine work?

A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.

How many types of vaccines are there?

There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.

What does it take to develop a vaccine of this kind?

Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.

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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.

The Beijing-based company has recently received new orders from Malaysia and the Philippines. Earlier, Singapore and Hong Kong had placed their order for CoronaVac.
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