Even if all the Georgetown undergraduates were somehow infected by Delta
and
mRNA reduces these both by .9.
mRNA vaccines don’t decrease hospitalisation by .9 given someone has become infected, they decrease it by .9 compared to an unvaccinated person given typical community exposure. So I think your calculation is more like “Even if all the Georgetown undergraduates were exposed to Delta in a way which would be sufficient to infect them if they were unvaccinated”.
I would estimate that to get back to your original scenario we probably have to multiply by 3-5 (depending on how much of the resistance to hospitalisation you think is purely resistance to getting infected in the first place).
and
mRNA vaccines don’t decrease hospitalisation by .9 given someone has become infected, they decrease it by .9 compared to an unvaccinated person given typical community exposure. So I think your calculation is more like “Even if all the Georgetown undergraduates were exposed to Delta in a way which would be sufficient to infect them if they were unvaccinated”.
I would estimate that to get back to your original scenario we probably have to multiply by 3-5 (depending on how much of the resistance to hospitalisation you think is purely resistance to getting infected in the first place).
Good point! I’ll edit my fermi analysis to reflect that.