A nurse holds her arm after receiving the Sinovac vaccine in Hong Kong. Photo: Peter Parks / AFP

The effectiveness of China’s Sinovac vaccine, now widely used across China and donated to the developing world, remains an enigma. But preliminary indications that the shot is less effective against the Delta variant now surging worldwide are ringing alarm bells.

Singapore has stopped recognizing takers of the Sinovac jab in its national vaccination tally, citing “insufficient data” of its protection.

Hong Kong, one of the few jurisdictions where those from Sinovac and Western suppliers are both rolled out for people to choose, has also tacitly recommended the messager ribonucleic acid (mRNA) shot from BioNTech in Germany. 

Thailand is now recommending that those who received a first jab of Sinovac take a second shot of AstraZeneca to improve protection particularly against the Delta virus, which is now spreading in the kingdom.

The wider rollout of Chinese jabs and the World Health Organization’s (WHO) recent inclusion of Sinovac’s vaccine on its approved list has added to the confusion.

Earlier estimates of Sinovac’s efficacy reported by countries that carried out final-stage trials varied much more widely than Western-made drugs.

One widely quoted estimate, from Brazil’s Butantan Institute in Sao Paulo, put it marginally above the WHO’s approval threshold of 50% once very mild cases were taken into account. 

Even Chinese state media have confirmed that some of those who contracted the strain during the southern city of Guangzhou’s resurgence in May and June had been fully inoculated with Sinovac.

The admission has thrown the drug’s efficacy into sharper relief now that a more transmissible variant has become the dominant version in much of the developing world, from Africa to Southeast Asia, that relies on Sinovac. 

The first consignment of Sinovac vaccine from Beijing is unloaded from a Cathay Pacific plane in Hong Kong in February. Photo: Handout

At the same time, Beijing has brushed aside some people’s growing doubts as it presses ahead with its nationwide immunization drive using primarily the Sinovac jab made at the company’s plant in the capital city, with experts stressing limited protection is better than nothing.

Close to 1.4 billion doses have been given nationwide as of Monday (July 12), according to a tracker updated by the National Health Commission, though the number of those fully vaccinated or the provenance of shots used is not specified. It is believed that the Sinovac jab has made up the lion’s share, though.   

Chinese state media and experts with the National Center for Disease Control (CDC) have since then pivoted to hail the Sinovac jab’s “outstanding” protection against severe comorbidities and fatalities, even if the drug may fail to shield recipients from the pathogen in the first place. 

Chinese papers also reiterate the data from Brazil’s Butantan Institute that the vaccine was 78% effective in mild cases and as high as “100% effective” against severe and moderate infections, based on 250 Covid cases among some 13,000 participants from Brazil’s health workers on the frontline treating the infected. 

An immunization planning expert with Shanghai’s CDC, commenting on the condition of anonymity as he was not authorized to speak to foreign media, told Asia Times that Sinovac’s shot is “partly good.”

“[The Sinovac shot] may look more like a “Covid medicine” people take in advance to lower the risk of serious cases, but takers may still need to stick to anti-epidemic rules and may need a booster shot,” he said.

He added a caveat about the seemingly more impressive figures. Trials in Brazil were conducted in 2020, before Covid had evolved into its new, more contagious variants. 

Gao Fu, the chief of China’s CDC, is now an advocate of the mRNA formula used in Moderna and Pfizer vaccines but still touts the Sinovac jab’s attributes in the developing world.

Unlike mRNA vaccines, Sinovac is cheaper to mass-produce, can just be kept in a home fridge and is much more stable to store. 

“These things matter when you’re talking about immunizing a population not just in the tens or hundreds of millions, but in the billions,” said Gao, who earlier this year urged Beijing to expedite its development and approval of homegrown mRNA drugs. 

A health worker administers Sinovac vaccine to a young woman in Gelora Bung Karno Stadium in Jakarta, Indonesia. Photo: AFP / Aditya Irawan / NurPhoto
Turkey’s President Recep Tayyip Erdoğan is vaccinated with Sinovac in January. Photo: Xinhuanet / CCTV

Mark Lynas, a senior researcher with Cornell University’s College of Agriculture and Life Sciences, wrote on a blog that the significance of Sinovac’s shot was its 100% effectiveness in preventing acute cases. 

“So if you want to save lives and stop health services from being overwhelmed, this vaccine is fine. If you want to eradicate Covid-19, perhaps it’s not quite good enough,” said the scholar.

“The inactivated virus approach has been used for decades against different diseases so it is very well proven in the real world but it may be slightly weaker than the newer approaches.”

Lynas pointed out that the levels of virus exposure among frontline health workers in Brazil who took part in the trials could be very high and therefore the Sinovac vaccine had “a tougher job” protecting them. He also added that the two doses were only spaced 14 days apart in Brazil but a better response may be achieved if the interval was longer. 

Former Brazilian president Luiz Inacio Lula da Silva receives a dose of the Sinovac vaccine in March. Photo: AFP / Paulo Lopes

The Sinovac debate has geopolitical undercurrents as well. Beijing raced against Western rivals to roll out vaccines last year and to donate or sell them to its diplomatic allies.

Western media portrayed this as “vaccine diplomacy” as Beijing was accused of attaching geopolitical demands to some of its aid. 

In the face of the threats from the Delta strain, the stakes are high when, according to a report by CNBC, at least five out of the world’s six most inoculated countries that are also reporting lingering or even rising infection rates rely on vaccines from China. 

The United Arab Emirates, Seychelles, Mongolia, Uruguay and Chile, all are recipients of Chinese vaccines, have all reported first dose coverage of 60% or higher, but also have more than 1,000 weekly new confirmed cases per million people as of July 6. 

Some of these countries also buy from China’s state-owned Sinopharm, whose vaccine has demonstrated a higher protection rate of about 75% in overseas trials. That said, the Sinopharm shot is less accessible due to production bottlenecks and deliveries to senior party and government officials as well as foreign dignitaries have thus been prioritized.

Chinese media reported that all the deputies of the Chinese parliament as well as the top political advisory body, the Chinese People’s Political Consultative Conference, received Sinopharm vaccines before this year’s plenary session in Beijing in March. 

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