Allow me to clarify my position on a theoretical emergency use authorization (EUA) for a #SARSCoV2 #COVID19 #coronavirus vaccine:

I think EUA is fine in such an urgent situation, provided that there is phase 3 safety and efficacy data to support it.

Some have responded to my tweet thinking that I am opposed to issuing an EUA for a vaccine AT ALL. That's not true. I strongly oppose issuing an EUA for a vaccine before we have any information about whether or not it actually works. https://twitter.com/angie_rasmussen/status/1300090439962296321?s=20

Here's how phase 3 clinical trials work: they enroll a lot of people (tens of thousands). Some randomly get the experimental vaccine, some get another unrelated, already-approved vaccine. These people then go about their normal lives.

In the course of those normal lives, some will be exposed to #SARSCoV2 and become infected. The trials follow up with participants periodically and tally up who has become infected and obtain data about their course of #COVID19.

After enough people from both the experimental and control groups become infected, you can use statistics to assess if there is a significant difference. Did fewer people receiving the experimental vaccine become infected? Of those who did, was their disease less severe?

If a significantly lower number of people receiving the experimental vaccine were infected and/or had less severe disease, that suggests the vaccine is effective at preventing infection (fewer infections) and/or ameliorating disease severity (less severe COVID-19).

Again, this is dependent on how long it takes for trial participants in both experimental and control groups to be exposed in the course of their normal lives. This may happen more quickly in places with high community transmission, but also depends on a lot of other things.

If participants are taking precautions to reduce exposure risk (which hopefully they are), that could also increase the amount of time it takes to get sufficient data to assess efficacy, but that's okay. We shouldn't tell participants to behave recklessly to speed up the trial!

Similarly, safety is also evaluated in phase 3 trials. How many participants have to withdraw because of adverse events? For some vaccines administered in a prime-boost regimen (2 shots spaced out over time), these might not be apparent until after booster shots. So...more time.

Some people may think phase 1 and 2 trials already look at safety. They do. But that still needs to be part of a phase 3 trial, since some rare adverse events may not be observed in smaller trials with fewer patients. Obviously safety is as critically important as efficacy.

So BOTH safety and efficacy are crucial to establish before a vaccine is authorized for public use, even for limited groups as Dr. Hahn suggested. Why? If a vaccine gets EUA and it either doesn't work or is a significant safety risk, it would cause tremendous harm.

If a vaccine isn't safe, it could harm all the people who take it. Even if it is safe, but isn't effective, it could indirectly harm people by giving them a false sense of security that they are protected. Both situations would be extraordinarily damaging to public health.

Issuing an EUA for a vaccine without safety and efficacy data to support that would deal a catastrophic blow to public confidence in both vaccines and the regulatory mechanisms in place for evaluating their safety and efficacy.

Vaccine skepticism and refusal are already huge public health problems. Providing public access to an unsafe or ineffective vaccine would discourage huge numbers of people from getting other vaccines that we already know ARE safe and effective.

Furthermore, if an EUA were issued for non-scientific reasons (like, say, a candidate's desire to have an edge in an upcoming election), it would destroy public trust in medical science as an evidence-based enterprise. We cannot let that happen.

Finally, it is unethical to conduct trials without the informed consent of participants. Scientists and physicians are trained in bioethics to ensure that they design trials to minimize harm to participants. Trials undergo ethical review at multiple stages.

Circumventing clinical trials by issuing an EUA without safety or efficacy would place huge numbers of people at risk for massive potential harm. It makes a mockery of the very serious protections put in place to conduct clinical research ethically.

We absolutely cannot tolerate or accept an EUA for any #SARSCoV2 #COVID19 #coronavirus vaccine without reliable safety and efficacy data from phase 3 clinical trials.