AstraZeneca has signed a three-year manufacturing deal with Oxford Biomedica to mass-produce its COVID-19 vaccine candidate AZD1222.

Under the agreement, AstraZeneca will pay $20 million to reserve manufacturing capacity from three sites in Oxford Biomedica’s Oxbox manufacturing center through 2021, with an option to expand the deal by an additional 18 months.

The deal expands on an existing commercial supply agreement that the companies signed in May for manufacture of the vaccine.