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.