in late april 2020, a team from oxford university announced that they had developed a covid-19 vaccine. the united states national institutes of health tested it in rhesus monkeys, and it worked. the oxford scientists said 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. the scientists said 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.