I was wrong: We can’t skip Phase 3 vaccine trials

On point (1), there are several risks that I didn’t emphasize sufficiently. One is that although phase 1 and 2 trials establish safety, they don’t tell the whole story. Phase 3 also looks at safety, and because many more subjects are involved, Phase 3 can identify less-common side effects that might still be very bad. (One example is ADE, which can make a viral illness worse than it would otherwise be.) These less-common side effects are a big risk of moving too quickly.

Another risk is that of trust: as many people pointed out on Twitter, if we expand the distribution of vaccines too quickly, and then the vaccine doesn’t work, we may seriously undermine the public’s trust in any eventual vaccine that really does work. That in turn will reduce the number of people willing to be vaccinated, which could cause serious harm to public health.

On the benefit side, my article assumed that we could quickly make millions of doses available before Phase 3 trials completed. I was wrong there too.