Chinese COVID-19 vaccine much less effective than initially announced in Brazil, raising concerns


A leading Chinese COVID-19 vaccine developed by Sinovac Biotech was only 50.38% effective in advanced-stage trials in Brazil, significantly lower than previous results, according to a statement released Tuesday by the government of Sao Paulo .

While that number exceeds the threshold required for regulatory approval, it falls well below the previously announced 78%, raising questions about the veracity of the data and fueling skepticism about the apparent lack of transparency regarding Chinese vaccines.

Sinovac’s Coronavac Vaccine Efficacy Rate Analysts Reported in Brazil – the lowest among its global competitors – could affect international confidence in Chinese-made vaccines and hamper Beijing’s efforts to repair its image after its early mismanagement of the initial outbreak by providing COVID-19 vaccines to developing countries.

“The Butantan Institute and the government of Sao Paulo report that the coronavirus vaccine achieved an overall efficacy rate of 50.38% 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 above the level of 50% required by the WHO (World Health Organization), ”said the statement released Tuesday.

The narrow margin for regulatory approval is likely to cause concern among scientists, given that last week the Butantan Institute published partial “clinical efficacy” results celebrating 78-100% efficacy in prevention infections.

The state body funded phase 3 trials of the vaccine, involving 13,000 health workers in eight Brazilian states.

“Regarding the overall efficiency of the analysis, we met the requirements of the World Health Organization with 50.38%,” said Tuesday Ricardo Palacios, medical director of clinical research at the Butantan biomedical center in Sao Paulo. at a press conference.

However, on Tuesday, senior members of the Brazilian health ministry told CNN affiliate CNN Brasil that “efficiency is at the limit” and “it is at the limit. assess. ”

A representative for Sinovac said the company was discussing the outcome but declined to give further comment. The vaccine’s final efficacy rate will be determined by China’s drug regulator, the National Medical Production Administration, according to the representative.


Yanzhong Huang, senior researcher for global health at the US-based Council on Foreign Relations, described the 50.38% effectiveness of the Sinovac vaccine as a “disappointing” result that surprised him.

The results suggest that Coronavac is less effective than the alternative vaccines developed by Pfizer-BioNTech and Moderna, which have an effectiveness rate of around 95%.

Russia claims its Sputnik V vaccine is 91% effective, while the British vaccine, developed by the University of Oxford and AstraZeneca, has an average effectiveness of 70%.

The Sinovac vaccine is also less effective than its Chinese national competitor, developed by state-owned Sinopharm, which it claims is 79.34 percent effective.

Despite the worse-than-expected results, Huang said the Sinovac vaccine would still be “usable” in helping to relieve pressure on health systems while reducing potential deaths, given its greater effectiveness for moderate and severe cases requiring. medical treatment.

However, its low overall efficiency could hamper Sinovac’s ability to expand its market share globally, Huang said.

Sinovac has signed agreements to deliver 46 million doses of its COVID-19 vaccine to Brazil, 50 million doses to Turkey and 7.5 million doses to Hong Kong. It will also supply 40 million doses of the vaccine in bulk – the vaccine concentrate before it is broken into vials – to Indonesia for local production.

“Since many countries are planning to order or have already ordered the vaccines from Sinovac, it could undermine people’s willingness to take them, as people may question the usefulness of the vaccines,” Huang said. “It could be a potential stumbling block. ”


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

Sinovac and Sinopharm faced questions regarding the release of the data. When announcing its efficacy results, state-owned Sinopharm did not provide details of its clinical trial data. A Sinopharm executive said detailed data would be released later and published in scientific journals, without giving a timeline.

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

After largely eliminating the coronavirus within its borders earlier last year, Chinese drugmakers have had to look overseas for places to test the effectiveness of their vaccines. But the results reported so far are far from consistent.

Sinopharm’s efficacy rate of 79%, for example, is lower than the 86% reported by the United Arab Emirates for the same vaccine in December.

Sinovac’s vaccine has had vastly different results in three countries: Indonesian drug regulators say interim data from Phase 3 trials have shown it to be 65.3% effective and have given it the first approval of emergency use of the country; Turkey says it is 91.25% effective; And in Brazil, the two significantly different efficacy rates announced a week apart still raised questions.

Last week, Brazil’s health regulatory agency ANVISA told the Butantan Institute that in order to approve emergency use of a vaccine, the global efficacy rate had to be made public – information that the Institute had not received at the time of Sinovac, according to Sources CNN Brasil.

ANVISA will meet on Sunday to decide on two requests for emergency use of the Coronavac vaccine and the AstraZeneca vaccine from the University of Oxford.


The news could also hamper China’s coronavirus vaccination campaign, Huang warned.

China has vaccinated tens of thousands of people with the Sinovac vaccine since July under a government-approved emergency use program, which includes at least three Chinese vaccine candidates.

In total, it has administered 4.5 million doses of the coronavirus vaccine for emergency use and plans to vaccinate 50 million people ahead of the Lunar New Year celebrations in February.

Chinese public health experts have repeatedly told the public that they believe Chinese-made vaccines are at least as good, if not better, than foreign alternatives, Huang said.

“If people find out about this, they might start to question the safety and effectiveness of the Sinovac vaccine, or even other vaccines made in China,” Huang said. “I think the government will have to do a convincing job, either on those who have already taken the photos or on the verge of doing so. ”


Please enter your comment!
Please enter your name here