Production of the coronavirus vaccine developed by French firm Sanofi and GlaxoSmithKline (GSK) will begin within weeks, the firms have said.
The two companies are currently in Phase 3 of their trials, which will see 35,000 adult volunteers receive their coronavirus jab across the US, Asia, Africa, and Latin America.
They will test for effectiveness against the original form of COVID-19 that swept across the world after emerging in Wuhan, China, in late 2019 - and also the variant first detected in South Africa.
"Manufacturing will begin in the coming weeks to enable rapid access to the vaccine should it be approved," a joint statement from Sanofi and GSK said.
The Sanofi-GSK vaccine could be given the green light by drugs regulators in the final three months of this year if the Phase 3 trials are successful.
It was originally due to be approved in the first half of 2021, but Sanofi and GSK were forced to restart trials in December after studies showed a poor immune response in the elderly.
The UK has ordered 60 million doses of the vaccine, joining existing supplies from Oxford-Astrazeneca, Moderna, and Pfizer-BioNTech, while the EU is depending heavily on the French firm for its supply - having ordered 300 million doses for use across the bloc.
"The design of the Phase 3 trial conducted across a broad diversity of geographies, also allows evaluation of the efficacy of the candidate against a variety of circulating variants," Sanofi said in a statement.
The company also said it would begin clinical studies in the coming weeks to see if the jab could also be used as a booster - regardless of what vaccine a person had originally.
Thomas Triomphe, who leads vaccine research and development at Sanofi, added: "We are encouraged to see first vaccinations starting to take place in such an important, pivotal Phase 3 study."
Separately, GSK is working with German biotech firm CureVac on a next-generation COVID vaccine that could be used against several new variants at once. They say they plan to launch the jab in 2022.