Novavax Inc. said on Tuesday its experimental COVID-19 vaccine produced high levels of antibodies against the novel coronavirus, according to initial data from a small, early-stage clinical trial, sending the company’s shares up 10%.

The company said it could start a large pivotal Phase III trial as soon as late September, and on a conference call added that it could produce 1 billion to 2 billion doses of the vaccine in 2021.

Novavax research chief Gregory Glenn told Reuters the late-stage clinical trial could potentially glean enough data to obtain regulatory approvals as early as December.