LONDON (THE FINANCIAL TIMES) - China's race to develop its own messenger RNA (mRNA) Covid-19 vaccine has gained greater urgency as Beijing struggles to rein in an outbreak of the Omicron variant that is threatening its zero-Covid policy.

Beijing's pandemic strategy, in which the authorities implement strict lockdown measures on communities with local cases to quash any outbreak, has, according to China's official statistics, proved effective at preventing the large number of deaths suffered in some Western countries.

But it has left China isolated from the rest of the world and confined millions of its own citizens to their homes to prevent the virus from spreading.

Progress towards a domestic mRNA vaccine in China has been slow, as the country's pharmaceutical companies opted initially to use traditional inactivated virus technology in vaccines.

In November, Chinese biotech company Suzhou Abogen Biosciences and its partner Walvax Biotechnology received regulatory approval to test their mRNA vaccine candidate in a booster trial.

Their vaccine deploys the same type of technology used in the Moderna and BioNTech/Pfizer jabs, which provide higher levels of protection against the Omicron variant than existing Chinese-made shots.

Dr Jerome Kim, director-general of the International Vaccine Institute in South Korea, said Chinese pharmaceutical companies had opted for the "old-fashioned vaccine" because the "existing technology was easily available and had been used in vaccines that had inoculated billions of people".

But researchers maintain that this method produces a weaker immune response than mRNA and viral-vector vaccines, which induce a targeted response to the virus's spike protein as it enters human cells, compared with the inactivated vaccine, which attacks many viral proteins.

China has administered 2.8 billion doses of Sinopharm and Sinovac's inactivated virus vaccines to 1.2 billion people. But the lockdown of 13 million residents in Xi'an, where more than 1,758 cases have emerged over the past month in China's worst outbreak since the start of the pandemic in Wuhan, has underscored officials' lack of confidence in domestic jabs.

"The lower efficacy of the Chinese vaccines indicates that most people lack the necessary neutralising antibodies to prevent infection or severe cases," said Dr Jin Dong-yan, a virologist at the University of Hong Kong.

Research from the university showed that two jabs and a booster of Sinovac's vaccine provided insufficient protection against the Omicron variant, while another study demonstrated that both Chinese vaccines' efficacy declined quickly.

In November, Chinese academics published a study warning that moving away from Beijing's strict zero-Covid policy to one similar to the United States would overwhelm the medical system and spell disaster for the country.

The low efficacy of Chinese vaccines has had repercussions beyond its borders, as Beijing has exported 1.49 billion shots.

One study of 185 healthcare workers in Thailand, which has not been peer-reviewed, found that 60 per cent of recipients of Sinovac jabs had high levels of neutralising antibodies one month after receiving their second jab, but that figure dropped to 12 per cent after three months.

Even as evidence of the weaker performance of its vaccines mounts, Chinese regulators have held off granting approval to the BioNTech mRNA vaccine. The German drugmaker has sought to enter the Chinese market through a distribution partnership with China's Fosun Pharma.

Dr Calvin Ho, a bioethicist at the University of Hong Kong, said Beijing had not recognised vaccines developed by foreign pharmaceutical companies because it wanted to support home-grown alternatives.

Investors are hoping the Walvax and Abogen vaccine, which is being developed alongside researchers from a Chinese military medical institute, will not face the same political barriers.

Last year Abogen, which was founded in 2019 and is based in Suzhou, west of Shanghai, raised US$1.1 billion (S$1.49 billion) from backers including Temasek, the Singapore state-backed investment fund, and investment firm Invesco.

Beijing has never authorised mRNA products for therapeutic use, putting domestic drug companies on the back foot as the strength of the technology became evident during the pandemic.

A leading Chinese respiratory disease expert, Dr Zhong Nanshan, said last month that China should "learn from other countries in areas they have done well, like mRNA vaccines. They have spent years developing it and managed to produce the mRNA vaccine in a few months".

Hong Kong university's Dr Jin said that, because China was slow to develop mRNA technology, its pharmaceutical companies lacked the scientific know-how and specialised machinery to deliver the jab at scale.

He added that there were significant technical barriers to making lipid nanoparticles, the fatty shield that protects fragile mRNA molecules when entering human cells, which are difficult to create safely and in large quantities.

But Dr Kim said that it was only a "matter of time" before China has access to an mRNA vaccine and that the safe and effective lipid nanoparticles were available to be licensed if domestic companies could not produce their own.

Pre-clinical trial data showed the Walvax and Abogen vaccine candidate, which is called ARCoV, produced a robust antibody response against coronavirus during the animal testing phase. No data on the more conclusive later-stage trials on human subjects has been published.

But even if China rolls out an mRNA vaccine as a booster, experts warned that it may not be a silver bullet that gives the authorities the confidence to end its zero-Covid policy.

An immunology professor from Beijing, who did not want to be named, said that even if China rolled out its own mRNA vaccine, "it wouldn't have a big impact on China's pandemic control measures" since evidence from existing versions of the jab showed that breakthrough infections are still possible.