in late april 2020, a team from the university of oxford said that they had developed a covid-19 vaccine. the united states national institutes of health tested it in rhesus monkeys and it worked. because they had already been working on a vaccine against a different coronavirus, they had a head start working on one for sars-cov-2. they would try to test their vaccine on 6000 people by the end of may 2020, and that their vaccine could be ready for people to use in september 2020.