AstraZeneca has expanded an agreement with Oxford Biomedica to scale up production of its potential Covid-19 vaccine, as the race continues to find an effective prevention for the deadly virus.

Under the supply agreement, the Oxford-based cell and gene therapy firm said it would produce tens of millions of doses of AstraZeneca’s potential vaccine, AZD1222, for 18 months, which could be extended by a further 18 months into 2023.

It will be made at the firm’s three manufacturing suites at its new centre, Oxbox, in Oxford. Two of the suites will be ready to use in the next two months, earlier than expected. AstraZeneca will pay Oxford Biomedica £50m under the deal.

AstraZeneca, which is developing the vaccine with researchers at Oxford University, said its global manufacturing capacity was close to 3bn doses.

News of the deal came as AstraZeneca announced on Monday night that it had begun late-stage trials of the vaccine in the US, where it plans to enrol 30,000 adults, as part of a global programme to test the product on 50,000 people.

AstraZeneca, along with US company Pfizer and its German partner BioNTech which are also developing a coronavirus vaccine, have said they could have data by October to secure approval from US regulators for emergency use of their respective products.

Last week, scientists raised hopes that trials of the Oxford vaccine could have gathered enough data to show whether it works and is safe by the end of the year, before being submitted to UK regulators for approval.