While a laggard in the global vaccine industry, China, where the new coronavirus is thought to have originated, has brought state, military and private sectors together in a quest to combat a disease that has killed over 500,000 people worldwide.

Many other countries, including the United States, are coordinating closely with the private sector to try to win the vaccine development race, and China faces many challenges.

Its success in driving down COVID-19 infections makes it harder to conduct large-scale vaccine trials, and so far only a few other countries have agreed to work with it. After past vaccine scandals, Beijing will also have to convince the world it has met all safety and quality requirements.

But China's use of command economy-type tools is so far yielding results.

A state-controlled entity, for example, completed two vaccine plants at what it called the "war time speed" of a couple of months, while state-owned enterprises and the military have allowed experimental shots to be used on staff.

The People's Liberation Army's (PLA) medical research unit, which has been a driving force in China's efforts to fight infectious diseases, is also working with private firms including CanSino to develop COVID-19 vaccines.

Challenging the West's traditional dominance of the industry, China is behind eight of the 19 vaccine candidates in human trials, with Sinovac's experimental shot and one jointly developed by the military and CanSino among the front runners.

It is also focused mainly on inactivated vaccine technology - a technology that is well known and has been used to make vaccines against diseases such as influenza and measles - something which could raise the chances of success.

By contrast, several Western rivals such as US-based Moderna and Germany's CureVac and BioNTech are using a new technology called messenger RNA that has never before yielded a product approved by regulators.

'"It's a tried and true strategy," said Paul Offit, director of the Vaccine Education Centre at Children's Hospital of Philadelphia, about inactivated vaccine technology.

"If I had to pick a vaccine that I think would be the most likely to be safe and effective, it would be that one," he said. Offit is also co-inventor of the rotavirus vaccine, RotaTeq, manufactured by Merck & Co Inc.

Four of the Chinese candidates in human trials are inactivated vaccines, including Sinovac's and two vaccines from China National Biotec Group (CNBG), a unit of state-owned China National Pharmaceutical Group (Sinopharm).

There are currently only two experimental COVID-19 vaccines in final Phase III trials - one from Sinopharm and another from AstraZeneca and the University of Oxford. Sinovac's is set to become the third later this month.

To speed up the process, China allowed Sinopharm and Sinovac to combine Phase I and Phase II trials for their vaccine candidates.

For CanSino's experimental vaccine, the PLA research institute played a key role, with the two working on a method using an adenovirus - a similar approach to AstraZeneca's.

The PLA has its own approval process for "military specifically-needed drugs", and approved the military use of the candidate developed by its research unit and CanSino last month.

PLA lead scientist Chen Wei, who has been the face of its vaccine development effort, was among the first to take the experimental COVID-19 shot developed by her team, as well as its potential SARS treatment years before, according to state media.

China has challenges, though, as the epidemic has petered out in the country, hampering efforts to conduct large trials.

It has since shifted its focus overseas, but only a handful of countries have shown willingness to collaborate - UAE, Canada, Brazil, Indonesia and Mexico. Neither major European countries nor the United States have shown interest in China's COVID-19 vaccines as they focus on their own projects.

China must also address concerns over its vaccine quality and safety issues following several scandals over substandard vaccines in recent years.

"The Chinese national regulatory authority has been improving its oversight," said Jerome Kim, head of the International Vaccine Institute, a non-profit agency established as an initiative of the UN Development Program.

China introduced a law last year to regulate the vaccine industry, with heavier penalties for selling and making fake or low-quality vaccines than other drug products.

Australian Associated Press