Serious Concerns Raised Over Substandard Chinese Covid-19 Vaccine


  • Chinese Covid-19 vaccine far less effective than initially claimed.
  • Efficacy of Sinovac Biotech advertised at 78%, new data show it's only 50.38% effective.
  • A lack of transparency has been a major concern clouding Chinese-made vaccines.

Chinese Covid-19 vaccine developed by Sinovac Biotech which was touted to be 78% effective against Coronavirus has been established to have an efficacy of 50.38%.

A statement published by the government of Sao Paulo in Brazil indicates that the efficacy of the Chinese vaccine falls far below the 78% previously announced.

“The Butantan Institute and the Government of Sao Paulo report that the coronavirus vaccine achieved a 50.38% overall efficacy rate in the clinical study conducted in Brazil, in addition to (an efficacy rate of) 78% for mild cases and 100% for moderate and severe cases of Covid-19. All rates are higher than the 50% level required by the WHO (World Health Organization),” the statement released Tuesday said.

Analysts said the efficacy rate of Sinovac’s Coronavac vaccine in Brazil is the lowest among its global competitors.

Pfizer-BioNTech and Moderna have an efficacy rate of about 95%. Russia says its Sputnik V vaccine is 91% effective, while the UK’s vaccine, developed by Oxford University and AstraZeneca, has an average efficacy of 70%.


The new data from Brazil could affect international confidence in Chinese-made vaccines. China has promised millions of coronavirus vaccines to countries globally.

A lack of transparency has been a major concern clouding Chinese-made vaccines, which Chinese President Xi Jinping has pledged to make a global public good.

Both Sinovac has faced many questions regarding the release of data. When announcing its efficacy results, it did not provide details on its clinical trial data.

A Sinovac executive said detailed data would be released later and published in scientific journals, without giving a timeline.

There is also the issue of discrepancy in results from clinical trials conducted in different places.

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