China administered its billionth dose of Covid-19 vaccine over the weekend, an important milestone for the world’s largest inoculation programme as it seeks to protect the country from imported infections. It follows a significant stepping up of the national vaccination programme , with the daily number of jabs passing the 20 million mark on multiple days in recent weeks and the overall number doubling since May 23. The National Health Commission announced on Sunday that the country passed the symbolically important landmark the previous day. The sheer volume is unmatched globally, with China accounting for more than one of every three doses administered so far worldwide, according to Bloomberg. Total global vaccinations topped 2.5 billion last week, according to the agency, at a rate of 37 million a day as of Friday. China’s average daily doses this month come in at over 18 million, with the highest single day total recorded on Friday when over 23 million doses were administered. “It is really an impressive scale – the roll-out and [production] scale behind it are equally impressive,” said Zoltán Kis, a research associate at the Future Vaccine Manufacturing Hub at Imperial College London’s Centre for Process Systems Engineering. China has set a goal of vaccinating 40 per cent of its 1.4 billion population before July, and aims to reach at least 70 per cent of the target population by the year’s end, so far relying exclusively on home-grown vaccines. But it faces an uphill challenge with the world’s largest population, and it remains unclear how much of the population is fully vaccinated, as data is rarely further broken down. Earlier this month officials made the rare disclosure that 622 million people had received shots of June 10, but did not specify how many had received a full course. Five of the seven vaccines authorised for market or emergency use require two doses, which can be administered up to eight weeks apart, and another needs three shots. The campaign has gathered more urgency following recent local outbreaks, including in the major southern port city of Guangzhou and surrounding Guangdong province , where over 100 cases have been identified since late May. “Recent local cases show that the epidemic prevention and control situation remains grim,” National Health Commission deputy head Zeng Yixin told the official Xinhua news agency earlier this month. “We need everyone’s help to build a ‘great wall of immunity’.” China’s vaccine makers have leaned on their experience of mass-producing other vaccines that use similar technology to ramp up capacity. “Both Sinopharm and Sinovac have been making inactivated vaccines [made using pathogens grown and killed in a lab] for other viruses, for example the hepatitis A virus, for a long time, so they do have the capacity and the expertise but making this huge volume of vaccines is not easy,” said virologist Jin Dong-yan, a professor at the University of Hong Kong. “They can scale up easily, that’s not an issue,” he said. The challenge, he added, was maintaining the strict quality control monitoring required to maintain the efficacy of the inactivated vaccines, which unlike some other vaccines require special biosecure facilities. Kis said that the ability to administer 20 million doses daily was tied to a complex logistical process. “These vaccines that are made in China are produced using more conventional technologies, most of them are inactivated viral vaccines, [and] these are slower processes, so it’s even more difficult to produce a number of vaccines rapidly,” he said. China’s vaccine makers could make at least 3 billion doses in 2021, according to some estimates. Feng Duojia, president of the China Vaccine Industry Association, earlier this year projected that 5 billion doses could roll off factory lines in 2022 and some executives from vaccine makers say the figure could be even higher. A projection by British life sciences analytics firm Airfinity last month pegged total global production of Covid-19 vaccines this year at over 11 billion, with Sinovac in the top three with 1.35 billion doses. The forecast was behind only the 2.47 billion doses estimated for BioNTech and Pfizer’s jab, and 1.96 billion for a vaccine developed by AstraZeneca. Of the three, Sinovac recorded the lowest efficacy rate as reported in World Health Organization documents, at 51 per cent or just above the WHO’s minimum threshold. Helen Chen, Greater China managing partner of LEK Consulting, said she expected Chinese producers were “running flat out”. “China could easily produce over 2 billion, and probably closer to 3 billion doses in 2021,” she said. Seven vaccines have been cleared for use in China. Four have been given market approval, including two inactivated vaccines by state-owned Sinopharm and one by Sinovac, as well as a viral-vectored jab by CanSino Biologics. Three vaccines – made by Anhui Zhifei Longcom, the Institute of Medical Biology of the Chinese Academy of Medical Sciences and Kangtai Biological Products – have been given emergency use authorisation. From a slow start in its early months, China’s public vaccine roll-out, which officially launched in December, has expanded from adults in high-risk jobs to the general adult population and then the elderly in good health, with the pace picking up significantly last month. Officials earlier this month indicated children as young as three would be included next. “Once you have the political will, once the top leaders send a clear message that this is the priority, and this has to be done, then it will be done,” said Yanzhong Huang, a senior fellow for global health at the Council on Foreign Relations in New York. He compared the approach to the mass mobilisation of resources to respond to China’s first outbreak in Wuhan and sporadic outbreaks since then. On the ground, this mobilisation has included makeshift vaccination centres in gymnasiums, neighbourhood associations offering information, mobile registrations and some local incentives ranging from shopping vouchers to free eggs. Reports of housing and commercial complexes asking for proof of vaccination have circulated on social media, but the authorities have not made it compulsory. China pledges joint Covid-19 vaccine production plan with Indonesia Officials and public health experts have stressed the need to reach a critical threshold of vaccinated people, upwards of 80 per cent of the population by some accounts, for there to be community-level protection or a chance to re-evaluate strict border controls. “The best method to prevent Covid-19 is vaccination. If a group reaches a threshold of immunity, through vaccination, then they can reduce the prevalence of the virus or stop its spread,” Wang Huaqing, chief immunologist at the Chinese Centre for Disease Control and Prevention, said earlier this month. But Huang said it may be difficult to maintain China’s current daily vaccination rate as some people remain reluctant to get jabs. He added that as the programme shifted to the countryside “it becomes more challenging to reach that segment of the population, that could include those people who are elderly and are the most vulnerable”. Meanwhile, questions remain about how long protection from the vaccines will last and their ability to respond to variants of the virus or block transmission. Huang also said that even when a high proportion of the population was vaccinated it would not completely block the risk of transmission, and it remained to be seen the extent to which Beijing would relax its stringent controls and accept some local cases at that point. “Even though you achieve herd immunity, there is still the question of what that’s going to mean for the zero-tolerance policy,” he said.