A production line for the Sinovac vaccine in Beijing. Photo: Xinhua

China’s frontline medical staff and at-risk groups including airport workers and even athletes and journalists are now asking for more protection against more infectious variants of Covid-19 including the Delta strain.

The calls come after the National Health Commission (NHC) admitted that a noticeable portion of those infected with the Delta strain in recent outbreaks in southern China had been fully vaccinated with indigenously produced shots. 

The Chinese General Administration of Sport made full vaccination compulsory for Chinese reporters traveling to Japan to cover the Olympics, with the option of receiving a booster shot. Some opted to roll up their sleeves for a third time, despite concerns about side effects.

Chinese reporters told state broadcaster China Central Television prior to their trip that they would be taking no chances in Tokyo, which is currently under a Covid-19 state of emergency. The Games throw together delegates from across the globe, including participants from nations still deep in the grip of Covid-19.  

Those opting for a third jab were given the same type of inactivated vaccine as their first two doses from Chinese pharmaceutical giants Sinovac and Sinopharm.

A staff member at a factory built to produce a Covid-19 vaccine at Sinovac, one of 11 Chinese companies approved to carry out clinical trials. Photo: AFP / Wang Zhao

Experts and policymakers are also working on a new strategy to further shore up China’s vaccine coverage and form a feasible cocktail of different vaccines to produce better and prolonged protection. 

The first group of people who had the homemade vaccines is nearing the end of the “optimal protection period” of about six months, according to reports. This has led to questions and debates about the need for additional jabs. 

Shao Yiming, a senior researcher with the Chinese Center for Disease Control (CDC), told China News Service and Caijing magazine that antibody levels should determine if people’s acquired immunogenicity against the virus would need to be fortified with more injections. 

Shao added that his research showed that about half of those vaccinated, mostly human trial participants who were given indigenous vaccines before the nationwide roll-out in the first quarter, had since seen overall antibody density drop to levels “inadequate to neutralize the Covid pathogen.”

Shao also said higher antibody levels would “definitely help” the body fight off new strains, including the more contagious Delta variant that is slowly but surely creeping into China.  

His remarks were echoed by Sinovac president Yin Weidong, who argued that three doses of the attenuated shots from his company could guarantee high and lasting antibody levels if dosing is properly spaced, preferably three to six months between the second and third injections.

Yin also said longer intervals between each shot could automatically strengthen potency, a statement that challenged a previous CDC advisory that warned one dose or belated follow-up injections could raise the risk of infections. 

Sinovac’s shots are facing growing scrutiny abroad as fully vaccinated health workers, including in Indonesia and Thailand, suffer “breakthrough” infections. Meanwhile, overseas third-stage human trial data suggest Sinovac’s overall efficacy rate could be as low as 50%. 

Singapore has stopped counting those taking the Sinovac shot in its national tally of vaccinations, while studies by universities in Hong Kong also suggest the necessity for an additional jab for adequate protection.

In a turn, Chinese CDC director Gao Fu recently applauded the “unique forte” of the messenger RNA (mRNA) vaccines in beating the original Covid strain as well as its latest variants.

The mRNA formula is being widely administered in the West, with Pfizer-BioNtech and Moderna’s shots increasingly seen as the global gold standard for shots.

Two men after receiving the Sinovac vaccine on June 24, 2021, in Singapore. Singapore allowed the usage of the Sinovac vaccine under the Special Access Route framework even though the vaccine remains unregistered and is not authorized by the Health Sciences Authority. Photo: AFP / Suhaimi Abdullah / NurPhoto

Jiangsu’s provincial CDC launched research in May to compare the antibody levels of those taking two doses of the traditional inactivated vaccines and volunteers given one more shot of a different type. But no foreign mRNA vaccine was chosen as Chinese drug watchdogs are yet to greenlight their use in the country.  

That could soon change, however, with growing indications regulators may soon fast-track their approval. 

Shanghai Fosun Pharma, the exclusive distributor of Germany’s BioNTech for the Greater China Region, last week said it expected “a quick turnaround” from Chinese authorities to let Germany-made mRNA vaccine enter the country. It is likely to be used as booster shots. 

However, CDC experts are reportedly split over whether a third shot, regardless of the type, should be made mandatory for all vaccinated Chinese. The preliminary consensus is that the general public should be allowed to decide for themselves.

The NHC’s latest data shows that China’s total vaccinations hit 1.5 billion doses as of Thursday (July 22), though there is no specific breakdown of those fully vaccinated or even given three doses. 

A girl gets her first dose of Covid-19 vaccine at a community center in Guangzhou. Nearly all of the vaccines being administered across China are supplied by Sinovac and Sinopharm. Photo: Handout

A scientific committee convened by Hong Kong’s government recently concluded that it was too early to confirm if and when a third dose would be needed for the general population.

“Achieving a high vaccination coverage as soon as possible and continuing robust non-pharmaceutical interventions to minimize the chance of viral transmission remain a priority in controlling the epidemic and preventing the emergence of more variants,” noted a report from the Hong Kong panel. 

“Both BioNTech’s mRNA and Sinovac vaccines are highly effective in protecting against severe conditions and fatalities from Covid infections, which are generally related to T-cell response.

“The much-discussed antibody response is related to the prevention of infection and symptomatic disease, but such a response is more susceptible to new, emerging variants and therefore, such prevention may vary among different vaccines.”

The panel also said current evidence on the “interchangeability” of vaccines was limited. In exceptional situations where a recipient was unable to complete the series with the same type of vaccine, the panel said vaccination with another type may be considered on a case-by-case basis.

Read more: China set to add BioNTech to its vaccine arsenal