BEIJING (NYTIMES) - China has done everything in its power to keep the Covid-19 virus outside its borders and protect its people - almost.
It has kept cases and deaths remarkably low through a "zero-Covid" strategy that has involved tracking and tracing every case, closing its borders and locking down cities of millions of people. It fostered domestic vaccines that allowed the country to carry out a massive inoculation effort.
But two years into the pandemic, China's 1.4 billion people still don't have access to one of the most effective coronavirus vaccines the world has to offer. Those vaccines use the breakthrough mRNA technology that was developed and approved in the West, and they have been embraced by dozens of countries.
The effectiveness of Chinese vaccines has been in doubt - partly because they use a century-old method for inoculation. Last spring, the country said it would approve BioNTech, the German mRNA shot made in partnership with Pfizer. Months later, China said it was also close to producing its own mRNA vaccine. Neither are available today.
China's lack of an mRNA shot - and its delay in approving a viable foreign option - has poked holes in Beijing's victorious pandemic narrative and prompted experts to question whether the country's go-it-alone approach is less triumphant than officials would have the world believe.
Under Mr Xi Jinping, China's President, the country has turned more inward, promoting self-reliance and championing development in areas such as semiconductors and other technology. The delay in recognising a foreign mRNA vaccine now appears to be a part of that deeply political exercise.
China is so committed to competing with the United States and the West on science and technology that some in the scientific community say it is hard to imagine that the state hasn't pulled out all the stops to develop a home-grown mRNA vaccine. That China has fallen behind on that front, and failed to approve a readily available foreign option, has left many experts baffled.
"We don't know how decisions are made nowadays in China, but a better vaccine would definitely help in maintaining a zero-Covid policy," said Dr Jin Dongyan, a virologist at the University of Hong Kong who has urged his peers in mainland China to approve the BioNTech vaccine.
"They are presenting to the world that they are doing well in vaccine development," he said of officials in Beijing. "And it would be embarrassing for them to show the opposite to the Chinese people."
China says its virus policies, which include strict lockdowns, have prevented millions of people from getting sick. But as a consequence, scientists say, the population has not built up enough natural immunity to help fight severe infection, making reliable vaccines even more crucial. And there is slowly mounting pressure on the country to pursue a new approach.
In recent months, officials have begun openly discussing the need to introduce better vaccine technology.
"We should learn about the good things in other countries, such as mRNA vaccines," Dr Zhong Nanshan, China's top respiratory scientist, said at a conference in December. "They have spent years on the research and managed to develop mRNA vaccines in just a few months."
China last week approved for emergency use a Covid-19 pill made by Pfizer called Paxlovid, a move that some experts said could help change Beijing's pandemic strategy.
It wasn't that long ago that China appeared ready to introduce an mRNA vaccine for Covid-19. Shanghai Fosun Pharmaceutical, BioNTech's Chinese partner, told investors last year that regulators would approve its mRNA vaccine for use in China by July 2021. The company, which had conducted clinical trials in late 2020, said that it could make as many as a billion doses a year.
That optimism has since faded. Chinese authorities now say they are still reviewing documents in order to "make a final decision on the approval of our vaccine", a spokesman for BioNTech said.
The approval process for Sinopharm and Sinovac - which manufacture the vaccines that are available in China - looked much different. Chinese regulators changed the rules to allow both Chinese drugmakers to submit their trial data behind schedule. Sinopharm's vaccine was approved a week after the company filed its application, in December 2020.
Vaccines from Sinovac and Sinopharm help prevent hospitalisation and death, but their ability to reduce transmission with variants such as Omicron is still in question.
Sinovac has shown to be only 51 per cent effective against preventing symptomatic disease, according to scientists in Brazil. The World Health Organisation said Sinopharm has an efficacy of 78 per cent.
Although the WHO has signed off on both Chinese vaccines for emergency use, most Western governments favour mRNA technology.
As approval for BioNTech languished, China said it was close to producing a home-grown mRNA shot called ARCoVax. Two private drugmakers and China's Academy of Military Medical Sciences said they were preparing to make 200 million doses by October, a Communist Party newspaper reported in September.
Had that happened, it would have been a remarkable achievement for China.
Unlike traditional vaccines that use an inactivated virus to trigger a response by the immune system, mRNA vaccines use a genetic molecule that assists cells to make proteins that can set off an immune response in the body. This response creates antibodies that are then used to fight the virus.
The first mRNA vaccines for the coronavirus were based on research conducted over decades by scientists in different parts of the world. It took the Western pharmaceutical companies Pfizer, BioNTech and Moderna just over a year to take those advances and apply them to a new kind of vaccine able to prevent serious illness and death from Covid-19.
The final version of the mRNA vaccines produced by Pfizer and Moderna came together with the help of a multi-billion-dollar programme under the Trump administration called Operation Warp Speed. The Food and Drug Administration determined in 2020 that the BioNTech vaccine has an efficacy rate of 95 per cent.
"This is not trivial technology," said Dr John Moore, a virologist at Weill Cornell Medicine. "So trying to reverse engineer it from scratch is one of those things where you ask, 'What could possibly go wrong?'"
If China is pursing a programme similar to Operation Warp Speed, it has not said anything about it publicly. One of the private companies helping to develop ARCoVax is Suzhou Abogen, a start-up founded in 2019 by a scientist who used to work at Moderna. Before the pandemic, Abogen was developing mRNA drugs for cancer, one of China's biggest epidemics.
The other drugmaker, Walvax, is a publicly listed pharmaceutical group. The two companies' partnership with the Chinese Academy of Military Medical Sciences suggests strong government backing, although Beijing has not mentioned an official collaboration.
Last year, the United States added the Chinese Academy of Military Medical Sciences to an entity list, a federal trade restriction list, accusing it of using biotechnology to support activities such as "brain control weaponry". The designation would make it difficult to export any final vaccine product it develops.
Researchers recently published the details of an initial trial of the ARCoVax vaccine involving 120 volunteers. They found it to be safe, and said it produced a moderate level of antibodies but caused more side effects, including fever, than the BioNTech shot.
Abogen and Walvax did not respond to requests for comment. A senior executive at Walvax told Reuters last month that it had recruited 28,000 people for a large, Phase 3 clinical trial. ARCoVax is also being tested as a booster.
A recent study showed that two doses of Sinovac boosted with an mRNA shot offered strong antibody protection against both the Delta and Omicron variants. But it is still unclear when the ARCoVax vaccine will be available in China.
And as the weeks go by, approval for BioNTech seems to grow more elusive.
"It's very difficult to predict actually when we will get approval," said Mr Sean Marett, chief business and commercial officer of BioNTech, speaking at a healthcare conference last month. "But China remains for us an extremely important market. We're very, very committed to it."