The shot was developed by Janssen Pharmaceuticals, a Belgium based division of Johnson & Johnson. It would be the first COVID-19 vaccine that only requires one dose.

Johnson & Johnson’s adenovirus-based vaccine works differently than Pfizer and Moderna’s vaccines, which use messenger RNA. Doctors say it produces an antigen, or protein, which causes an immune response to protect against the novel coronavirus. The same technology was used to develop the Ebola vaccine.