Was the Oxford vaccine effective? Forbes' take, at best it can said to provide partial protection. The monkeys were infected by the virus, but didn't grow symptoms. Success would have been declared, had their immunity killed off the virus as soon as it touched blood stream, like how all other vaccine's success is measured.
Lets wait.
https://www.forbes.com/sites/williamhaseltine/2020/05/16/did-the-oxford-covid-vaccine-work-in-monkeys-not-really/