Challenge trials for Covid-19 Delta variant

 Before the development of the first Covid vaccines, there was a good deal of discussion about the appropriateness of testing vaccines with human challenge trials, i.e. with tests in which volunteers were deliberately exposed to Covid so that the vaccine effectiveness could be more readily assessed.  Now, with the Delta variant spreading, those issues are once again live.

Only England has authorized challenge trials. Here's a story from the WSJ:

Researchers Ready Lab-Grown Covid-19 Delta Variant for Human Trials. U.K. company is growing the highly contagious variant under tight lab controls for use in challenge studies  By Jenny Strasburg

"While the rest of the world is trying to stamp out the Covid-19 Delta variant, British researchers are making progress growing a carefully controlled batch in a lab that they hope to use to infect volunteers in studies.

"The effort marks a new phase in the U.K.’s human challenge trials, the only Covid-19 studies in the world intentionally exposing participants to the virus with the goal of developing new vaccines and treatments. 

...

"Two Covid challenge trials sponsored by Imperial College London and the University of Oxford started earlier this year in the U.K. They so far have exposed more than 40 healthy, young volunteers under isolated medical supervision to the original Wuhan strain that circulated widely in 2020.

"Since then, the highly transmissible Delta variant has come to dominate infections globally, rendering vaccines less effective and boosting case numbers across the U.K., U.S. and elsewhere. Delta’s fast rise led researchers and U.K. challenge-trial partner hVivo Services Ltd. to focus on trying to grow the variant in the lab.

...

"It took U.K. researchers and government advisers almost a year to plan and gain approval from a U.K. ethics committee and medicines regulators to start the controversial challenge trials for which the Delta strain could eventually be used. The government provided funding; so did the London-based Wellcome Trust, a large healthcare-focused charitable foundation.

...

"The challenge trials faced pushback from some U.K. academics and foreign researchers, as well as from some government officials, who considered them unsafe or otherwise unethical, people involved in the process say. Delays have caused friction among partners. hVivo, part of London-listed pharma-services company Open Orphan ORPH 3.08% PLC, had hoped to use the Covid-19 challenge-trial model by now to test antivirals and other products for drug companies, executives have told industry peers. A U.K. government spokesman said the pace of the challenge studies has reflected appropriate caution, and the trials have been safe.

"Challenge trials have been used for decades to study viruses and other pathogens by deliberately exposing volunteers and studying the body’s response. While scientists in the U.S. and Europe also pushed to do Covid-19 challenge studies, only the U.K. has moved forward."

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Other posts about challenge trials.