Oxford vaccine testers chase coronavirus to Brazil where it is rampant

The Oxford team has already recruited about 10,000 volunteers in the UK, who were split into two groups. One got the vaccine, the other a placebo. The scientists are now looking for evidence that the vaccinated cohort has been protected. An ideal result would see none of the vaccinated individuals becoming infected. But to prove that the jab works it is also necessary for unvaccinated volunteers — the number will be set by regulators and depend, in part, on the size of the cohort — to develop Covid-19. The likelihood of people becoming infected determines how long it takes to get a result. “If it’s low, it’s going to take you ages,” Trudie Lang, director of the Global Health Network at Oxford University’s Nuffield Department of Medicine, said. If there is little virus circulating your trial may run aground, leaving you without answers.