[valarauko]

That's true, but the FDA EUA specify that Pfizer & Moderna stick to the dosage regime as tested. It's very likely that a half dosage/reduced dosage might be deemed acceptable, but AFAIK no national authority has allowed a dosage regime deviation from what was tested in the Phase III trials. The closest would be the UK allowing upto a 12 week gap between doses of the Oxford vaccine. I agree that it's probably worth it to half the dosage and double the number of people who can be covered when initial supplies are so limited, but till the FDA makes that call, we have to stick to the dosage as specified.

[lisper]

No national authority has had to deal with a world-wide pandemic for the last 100 years. Treating this situation as if it were business as usual and following the normal rules may not lead to the best outcome.

[valarauko]

I don't disagree with you, but they also have to balance risk. They need numbers to work on, and those numbers barely even exist right now. The 2K in the Moderna trial who received the single dose is a statistical blip compared to the hundreds of millions for whom the FDA would make decisions.

The EUA is their attempt to manage the health risk to the population - an investigational vaccine using an entirely unproven novel technology stack poses some unbound risk (likely small), vs the benefit of an effective vaccine. Once we change the dosage, the effectiveness also become unclear, while the risk remains (eg, potential trace contamination with precursors in the lipid carriers triggering shock in a untested population subset. Perhaps prescription statins greatly reduce the effectiveness of the vaccine, etc etc). It's the job of the FDA to err on the side of caution and see risks where we would not. I agree with you that the situation is unprecedented, but I also do not blame the FDA for only working with the data they have. I suspect that Pfizer & Moderna will conduct Phase IV trials with different dosage regimes based on which the FDA can modify the terms of the EUA.