Manufacturing and distribution could prove to be another sticking point. While traditional inactivated vaccines are less complex, said Dr Chowdhary, the manufacturing process is slowed by the need for high security labs to grow live virus at the start of the process.
Also, China does not have a large scale and globally established vaccine export business like India, for example.
Even its domestic manufacturing capability is unclear. CNBG says it has constructed a new factory, doubling its capacity to more than 200 million doses a year, while Sinovac has a new plant in Beijing capable of producing roughly 300 million doses annually – but neither is enough to cover the country’s entire population.
The risk of antibody dependent enhancement
There is one great leveller in the vaccine race.
Vaccine makers of all nationalities face one particular significant hurdle, the spectre of which was raised when the Oxford vaccine was suspended last week: there is a risk that the antibodies created by a vaccine interact with those naturally acquired to spark a potentially dangerous adverse reaction. This is known as antibody dependent enhancement (ADE).
The problem for vaccine makers is testing for it. In most, perhaps all, the trials run to date, volunteers are screened ahead of time to check they have not got existing SARs-CoV-2 antibodies before being given a jab. They are then monitored for adverse reactions if and when they come into contact with the natural virus.
But Dr Chowdhary said there was a theoretical risk ADE could happen the other way round if someone previously exposed to the virus was then inoculated with new antibodies.
“It is only a theoretical risk. But in science, unless we can prove it’s not there, we don’t say it’s not there. And as far as I know, we haven’t done that yet,” he said.