The chief executive of AstraZeneca , which is developing a leading coronavirus vaccine with Oxford University, said it is too early to deliberately expose trial participants to the pathogen, but it may become an option if ongoing tests hit a snag.
The British drugmaker last week started phase 2 and 3 trials of the vaccine, looking to recruit around 10,000 adults and children in Britain.
A certain number of participants will have to become infected in the course of their normal lives to achieve a reliable reading from the study over the next few months.
So-called human challenge trials have been discussed as an alternative option by scientists, whereby vaccinated volunteers are infected intentionally.
"We are running against time. We are seeing already in Europe the disease is declining," Soriot told an online press briefing. "Very soon the disease intensity will be low, and it will become difficult, so we have to move very quickly."
"If the disease gets to a very low level, maybe challenge studies will have to be considered. But we felt it's too early today to do that," he added.
Companies and research institutions are currently working on more than 100 vaccines, about 10 of which are being tested on humans, in a bid to stop the respiratory illness that at present has no treatment and has killed about 350,000 people.
Soriot said some of the Oxford University team that started early-stage human trials of the vaccine in April to test for safety and signs of an immune response were already privy to initial results, and that publication was imminent.
"We should see the results very soon," Soriot said.
Oxford University has said that the read-out of the wider trials may take between two and six months, depending on how many participants still catch the virus in the face of public-health efforts to quell its spread.