Oxford-AstraZeneca is a COVID-19 vaccine developed through a collaboration between the University of Oxford and the pharmaceutical company AstraZeneca. It uses a modified version of a common cold virus (adenovirus) from chimpanzees to stimulate an immune response against the SARS-CoV-2 virus, which causes COVID-19. The vaccine is administered in two doses, typically given 4 to 12 weeks apart. It has been widely used in many countries and is known for being easier to store and transport compared to some other vaccines, making it a key tool in global vaccination efforts against the pandemic.