A coronavirus vaccine developed by CanSino Biologics Inc appears to be safe and induced a rapid immune response in its first human trial, Chinese researchers reported on Friday in The Lancet medical journal.

CanSino uses a weakened common cold virus called an adenovirus — and Friday’s study showed people whose bodies recognized that cold virus didn’t get as much of the presumed COVID-19 benefit. To avoid that problem, the Oxford vaccine uses an adenovirus that normally infects chimpanzees.

This vaccine did not cause any serious adverse effects, the researchers say, though they did report some side effects such as fever. Furthermore, blood samples from the 108 vaccinated adults showed so-called neutralizing antibodies and T-cell responses against the novel coronavirus, a sign of possible efficacy.

“These results represent an important milestone,” coauthor Professor Wei Chen from the Beijing Institute of Biotechnology said in a statement.

All 108 test participants were quarantined in a hotel for 14 days after vaccination, to ensure they weren’t exposed to the coronavirus during a study meant to track safety.

CanSino is awaiting results from 500 volunteers injected in a next-step study. In Britain’s soon-to-begin larger tests, researchers will address how Oxford’s shot will affect older adults, who are at high risk from COVID-19. Pollard noted that people over 70 often don’t get as much protection from vaccines as younger people.