Sinovac jab is 78% effective in Brazil after data confusion

The vaccine developed by China’s Sinovac Biotech Ltd. was found to be 78 percent effective against Covid-19 in late-stage trials in Brazil, the most definitive evidence so far on the shot’s efficacy after previous data sparked doubt and confusion.

The protection rate, confirmed by Sao Paulo state officials, was derived from Sinovac’s most advanced final-phase trials in Brazil involving about 13,000 participants. Coming after  data was withheld  at a progress update in late December, the rate is still below the roughly 95 percent effectiveness seen in cutting-edge mRNA vaccines developed by Pfizer Inc. and Moderna Inc. and being deployed in the US.

Sinovac’s CoronaVac vaccine was 78 percent effective in preventing mild cases of Covid-19 and 100 percent effective against severe and moderate infections, said Dimas Covas, director of the Butantan Institute that partnered with Sinovac to produce the shot locally. The trial saw about 220 participants infected—160 in the placebo group while almost 60 received the vaccine, Covas said.


While the latest disclosure provides a clearer indication of the vaccine’s efficacy, it wasn’t a complete picture. It wasn’t apparent how the Brazilian researchers calculated the efficacy rate, as officials didn’t provide a more detailed breakdown of the study—including information about age groups and side effects of the shot. They also didn’t specify when the full documentation will be published.

The Butantan Institute declined to elaborate further, saying it had no information beyond what was released at Thursday’s news conference. Beijing-based Sinovac didn’t immediately respond to calls and text messages seeking further information.

Chinese vaccine developers’ lack of timely and clear disclosures have contributed to a lack of trust in their shots. Conflicting and incomplete information from Sinovac’s trials last month created confusion over exactly how effective CoronaVac is in protecting people against developing Covid-19.

Still, the latest results indicate Sinovac’s vaccine offers significant protection against Covid-19, which may shore up confidence in the shot in countries like Indonesia and Brazil that have inked supply deals. The Butantan Institute plans to request emergency use authorization from Brazil’s regulator Friday, Covas said.

China is seeking to extend its geopolitical influence through vaccine diplomacy, and the disclosure on the Sinovac shot adds another vaccine to its arsenal.

While less effective than Pfizer and Moderna’s vaccines, CoronaVac is roughly in line with the 79.3-percent efficacy rate for state-owned developer China National Biotec Group Co.’s Covid vaccine.

Another shot by AstraZeneca Plc has shown mixed results—it was 90 percent effective when a half-dose was given before a full-dose booster, while two full doses showed an efficacy of 62 percent.

Fridge temperature

Sinovac and CNBG’s vaccines use an inactivated version of the coronavirus to stimulate the body’s immune response. They can be stored at refrigerator temperature, making them potentially better choices for distribution and use in the developing world than the mRNA vaccines, which require deep freezing.

China has already administered more than 4.5 million doses of its domestically developed vaccines under emergency use authorization given mid last year, and is  aiming to  inoculate 50 million people against the virus by early February, ahead of the annual Lunar New Year holiday. CNBG’s shot last week became the first to be approved for use in the  general public  in China.

Sinovac can make more than 600 million doses a year at its production facilities in China. The company has orders from countries where it is undertaking vaccine trials, including Brazil, Turkey and Indonesia, and will also supply Singapore and Hong Kong in addition to the Chinese mainland.

Confusing data

Brazil’s disclosure on the Sinovac trial results comes after weeks of confusion. Researchers in Brazil  delayed  releasing complete data on CoronaVac in late December, saying only that it was found to be more than 50 percent effective. São Paulo state Health Secretary Jean Gorinchteyn later said the vaccine didn’t reach 90 percent efficacy. Further confusing matters, Turkey said its clinical trial showed an estimated efficacy rate of 91.25 percent for CoronaVac, though that was based on only 29 cases.

The release of more definitive data on the vaccine’s efficacy was delayed because Sinovac needed to reconcile results from different trials using varying protocols, a person familiar with the matter told Bloomberg at the time.

Like some other vaccines, CoronaVac is given in two shots, 14 days apart. Brazil’s Butantan Institute is considering spacing them out by as much as 28 days to get more people their first inoculations quickly, Covas, the institute’s director, said.

Sao Paulo Governor Joao Doria is attempting to expedite inoculations as Brazil sees a resurgence of the virus and the central government delays on a concrete vaccination timetable. Almost 11 million doses of Sinovac’s vaccine have already been shipped to the country.

Doria, a political rival of Brazilian President Jair Bolsonaro, plans to obtain swift approval and begin vaccinating the state’s some 45 million people on January 25. Pressure from other governors led the health ministry to include the shot, which has been  publicly shunned  by Bolsonaro, in the country’s vaccination plans.

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