A bottle of Sinovac vaccine on display. Overseas trials of the Chinese drug have returned different but less than impressive efficacy rates. Photo: Xinhua

Efficacy questions about Sinovac Biotech’s Covid-19 vaccine are rising as shots are shipped to countries across the developing world for mass inoculation campaigns. 

Indonesia has joined Brazil in revising downwards earlier estimates of the Sinovac-produced CoronaVac’s effectiveness after reviewing findings from final-stage clinical trials. 

Indonesia’s state-owned drugmaker Bio Farma, a party to the trials, said last December that CoronaVac was as much as 97% effective when the nation took delivery of the first consignment of 1.2 million doses.

As questions were raised about the Chinese drug’s high efficacy rate, Sinovac clarified that the figure referred to the positive conversion rate of serum antibodies found among trial participants. 

On January 11, while green-lighting the emergency use of the Sinovac vaccine for at-risk groups as soon as this week, Indonesia’s Food and Drug Authority revealed a 65.3% efficacy rate, compiled from the latest trials in Bandung involving 1,620 volunteers. 

Penny Lukito, the chief of the Indonesia Food and Drug Monitoring Agency, said Sinovac’s CoronaVac had been cleared for emergency use after authorities reviewed preliminary local trial data, as well as those from Brazil and Turkey.

Indonesian President Joko Widodo took a dose of the Sinovac-produced vaccine as part of his nationwide vaccination drive to convince people to get shots.

Not responding to questions about the steep drop of the efficacy rate from Bio Farma’s initial statement of 97%, the food and drug chief instead quoted Widodo as saying the Chinese vaccine was “safe and halal,” or fit for consumption by Muslims.

Workers of Sinovac check the packaging of the company’s vaccine against Covid-19 at a plant in Beijing. Photos: Handout

Brazil’s state-backed Instituto Butantan, which organized trails in Sao Paulo, said last week that CoronaVac was 78% effective in mild cases and 100% effective against severe and moderate infections based on 220 Covid-19 cases from a pool of about 13,000 volunteers.

Also in December, Turkish authorities announced a CoronaVac efficacy rate of 91.25% from an interim analysis of 29 cases among 7,371 participants in the country.

Brazilian researchers and officials on Tuesday adjusted their overall evaluation of the Chinese vaccine.

They added that the less obvious protection seen on mild and asymptomatic patients among the 13,000 volunteers had significantly dragged down CoronaVac’s general efficacy rate from 78% to marginally above 50%, the World Health Organization-gazetted threshold for vaccine use.  

Instituto Butantan researchers’ data exposed trial findings of the Chinese drug to potshots and questions from the drugmaker’s Western peers.

The Associated Press quoted Australia’s Griffith University epidemiologist Dicky Budiman noting that the Brazilian institute did not disclose data such as results by age and gender or the number of asymptomatic volunteers in the sample.

The expert said these data were essential to assess and verify whether the shot would comply with safety standards. Sinovac has so far remained reticent as doubts about CoronaVac make the rounds.

The Beijing-based pharmaceutical startup that had its high-profile floatation on the Shanghai bourse’s Star Board in December has only said that it still needed more time to “analyze and work out the differences” in the data from trials in Brazil, Indonesia and Turkey.

The company has promised to publish more data this month. But perceptions the company is holding back vital details of the trials and their assessments are gathering momentum, particularly compared with the mor transparent research and development and regulatory approvals for Western-made vaccines from Pfizer, Moderna and AstraZeneca.

That said, these shots are from different technological paths and require different assessment protocols. 

Sinovac vaccine will be shipped to several nations for mass inoculations as soon as this month. Photo: Xinhua

A number of countries and regions including the Philippines, Singapore, Hong Kong, Macau, Ukraine, Bolivia and others that are not involved in trials have signed agreements with Sinovac or are in negotiations to secure doses.

Chinese state media stresses that the “growing list” of foreign buyers of Chinese vaccines is a vote of confidence as these jurisdictions must have conducted their own scrupulous evaluations. 

Hong Kong officials said on Wednesday that the city’s immunization scheme could be “paused for a while” pending on the outcome of mass inoculations in other jurisdictions and that experts vetting vaccines would not jump to any premature decisions.

The city’s 7.5 million residents will be allowed to pick from CoronaVac and Pfizer-BioNTech’s messenger RNA vaccine if bigger batches arrive this month. 

China’s National Health Commission said this week that approximately nine million doses have been administered throughout the country, which is now seeing the biggest wave of local infections in more than nine months.

However, the number of people who have been vaccinated with CoronaVac is unclear.

Asia Times reported last month that medical, customs, public safety and airport workers prioritized for injections in China had not been informed of the type or the producer of the shots they received. 

Still, even if the SinoVac drug offers less protection from the coronavirus than previously purported, its efficacy rate is still above the WHO threshold. The lower efficacy rate is unlikely to dent China’s ballyhooed vaccine development success story.

Another vaccine from the state-owned SinoPharm has been certified by China and the United Arab Emirates with an effectiveness rate of 79.3%.

A SinoPharm employee at a Beijing plant examines injectors of the company’s attenuated Covid-19 vaccine. Photo: Xinhua

The UAE Vice President Mohammed bin Rashid Al Maktoum was vaccinated with the SinoPharm drug in December. 

Zhang Wenhong, a Harvard-educated infectious disease expert with Shanghai Fudan University’s Huashan Hospital, told reporters that CoronaVac’s varying efficacy rates could be due to different approaches to trials of various sizes on different continents.

He said he accepted the conclusions by these countries that the vaccine would still offer a certain degree of protection against the virus. He added the fact that no severe side effects or complications had been reported in trials across Brazil, Indonesia or Turkey, which also gave credence to the drug’s safety.

“[CoronaVac] is an attenuated vaccine, developed with existing, time-tested technologies and is safer than other types in the West, because most of the vaccines already in use belong to this type … A vaccine must be first and foremost safe to use, before we focus on its effectiveness, and in this regard, CoronaVac is still above the WHO’s 50% baseline,” said Zhang.

An online survey of 5,000 Chinese netizens held by news portal NetEase in December found close to 70% of them would opt for Chinese-made vaccines when they were asked to choose from a pool of Chinese and Western-made drugs including Pfizer’s. 

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