Brazil’s Butantan Institute Completes Phase 3 SinoVac Study & Shares Results: Transparency for A Chinese Vaccine Candidate

Brazil’s Butantan Institute Completes Phase 3 SinoVac Study & Shares Results Transparency for A Chinese Vaccine Candidate

Vaccines out of China were produced, and approved, rapidly but actual transparency into true efficacy has been more challenging but recently the results of a large-scale clinical trial involving the CoronaVac vaccine were made public for the first time via the preprint server. Thanks to health authorities in Brazil, the world can have more insight into the vaccine. Investigators from the Butantan Institute as well as vaccine maker Sinovac and numerous Brazilian trial sites provided a breakdown of the over 12,000 clinical trial participants, actual efficacy rates for preventing the infection, severity levels and detailed adverse reactions combined with suggestions for vaccine candidate improvement. The world discovered back in January that Sinovac’s CoronaVac was 50.7% effective in preventing symptomatic COVID-19 and 83.7% effective targeting those “cases requiring assistance” and they declared in January 100% effective targeting moderate or severe cases. CoronaVac was conditionally authorized in China back in February along with three other vaccine products produced there. Chinese vaccine producers haven’t shared much data with the world leading to questions about why.

How does CoronaVac rank?

Its efficacy rate of 50.7% makes it the lowest of the COVID-19 vaccine candidates but according to the World Health Organization’s threshold for greenlight at 50% the vaccine candidate can progress. Note that Sinopharm, a Beijing vaccine producer’s vaccine is about 79% effective.

Brazilian Scientists Appear Satisfied

Recently Brazilian investigators posted in the non-peer review results of the large study that “Efficacy to prevent any symptomatic COVID-19 started at 50.7% and became more extensive as disease severity increased.” They also wrote the vaccine was “safe” and “well tolerated.”

What groups Authorized this Clinical Trial?

The Brazilian National Research Ethics Council (CONEP) and the Brazilian National Regulatory Agency.

Who sponsored the Study?

Butantan Institute

The Study

This study involved 12,396 health care professional participants receiving two injections at least two weeks apart. One group received the study vaccine and one group a placebo. The trial did expand to include subjects aged 60 and above. While the overall study had an average age of 39.5 the elderly accounted for 5.1% of the overall study. Longer intervals seemed optimal (e.g 28 days).

The vaccine candidate group reported more adverse events than the placebo group which isn’t a surprise. No severe events were reported and primary complaints involved pain in and or around the injection site, fatigue, etc.

Concerns Among Chinese

Writing for SixTone, David Paulk reported that many have fretted in China about the indigenous vaccine products—how good are they? A Are they safe and effective for those people aged 60 and above? What about pregnant women?  Although declarations were made based on small-scale trials reports Paulk, the dearth of data involving pregnant or lactating women raised ongoing questions.

Those concerned for pregnant women didn’t get sufficient answers from the Brazilian study as it involved only 632 elderly participants and pregnant or lactating women were excluded, reports the SixTone reporter.

Deaths not Related

The study population of 12,393 included three deaths including two individuals on the placebo and one on the study vaccine—this death resulted from drug overdose not related to the vaccine.

SinoVac Supplies to Brazil & Beyond

The Butantan Institute has supplied Brazilian health authorities with 38.2 million doses of CoronaVac. By April 7, Sinovac had reportedly distributed another 180 million doses to 30 mostly low-and moderate-income countries (LMICs).


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