Vaccine development takes a long time because there are many steps in the process. Researchers must ensure the vaccine is safe, causes the correct immune response without causing other problems, and is protective against COVID-19. There are many stages of tests both in the lab and then clinical trials. Usually those must be completed before wide scale production of vaccine doses can begin, but some vaccine-makers have collaborated with the government and engaged in "at-risk manufacturing," producing vaccine candidate doses without knowing whether the vaccine candidates will succeed in trials. In the past, this process has taken years, but experts are cautiously optimistic that a COVID-19 vaccine will be available in limited quantities toward the end of 2020, and more widely accessible to the general population by mid to late 2021.
Updated 20 October 2020