Not forcefully. He said paid volunteers. Why does the idea of challenge trials cause a furious reaction? Let's compare it to the space shuttle: 135 missions with 2 missions in which everyone died. That's a case fatality rate of 1.5% -- in the neighborhood of the Covid CFR. And I'd expect a challenge trial on young healthy volunteers to have a much lower CFR. Why is risking people for the shuttle OK, but risking people for a vaccine that benefits all of humanity not OK?