Thread by @drsanjaygupta

CNN has confirmed that the United States government is considering a challenge trial as a failsafe or “Plan D” as Dr. Anthony Fauci told me - So what is a challenge trial? 1/16

It is a controversial approach in which healthy people are vaccinated and then intentionally exposed to the virus. The rationale for a challenge trial would be to assess the effectiveness of a vaccine more quickly. 2/16

The typical approach is to introduce a vaccine trial in an area of the world where virus is circulating rapidly. You need tens of thousands of people enrolled in that part of the trial, known as phase 3. 3/16

If, for some reason, the virus is no longer adequately circulating, those trials cannot be completed, because there aren’t enough people enrolled. That’s when the challenge trial might be considered. 4/16

What we’ve learned is the US government is preparing for a potential challenge trial by asking laboratories to submit proposals to create a strain of the novel coronavirus. 5/16
cnn.it/3kKMBKT

The goal: to create a strain that would be consistent and measurable. That would allow scientists to expose volunteers to a predictable dose of consistent virus, measure their response and compare it to others. 6/16

More than 100 scientists wrote an open letter to the head of the NIH in July calling for such trials -- but others have voiced ethical concerns. 7/16
cnn.it/3gZ9mbI

“A single death or severe illness in an otherwise healthy volunteer would be unconscionable and would halt progress,” vaccine experts wrote last month. 8/16
bit.ly/3arVHHE

They also said it would be unethical to organize an experiment in which people were deliberately infected unless there was a treatment that can save lives, known as a “rescue drug” -- which does not exist for coronavirus. 9/16

Also, consider this: challenge trials would likely be done with healthy volunteers -- producing data that might not apply to elderly people and those with pre-existing conditions - some of the most vulnerable to the coronavirus and are prioritized to receive the vaccine. 10/16

Already more than 33,000 people in 150 countries have signed up to volunteer. 11/16
1daysooner.org

But, it would still take time to start a challenge trial, which includes the time it’ll take to create and manufacture a strain of virus they can control. Data would likely not be available until the end of the year. 12/16

@PeterHotez and @DrPaulOffit say there’s already enough virus naturally transmitting that we should be able to get answers from the phase 3 trials that are starting to take place. 13/16

But ethicist Art Caplan says, what if those initial vaccine trials don’t work and we have a limited number of volunteers then “we should be ready to pivot to challenge trials.” 14/16
bit.ly/3402gzX

Challenge trials have been used for influenza, malaria, typhoid, dengue fever, and cholera in the past. But, typically - rescue medications are available in case someone becomes severely ill. 15/16

Dr. Anthony Fauci emphasized that they have no intention to use the strain and it would only be for an “absolutely far out contingency.” “Quite frankly, I don’t think this is something we’re going to use,” Fauci said. 16/16