[feanaro]

This is the right conclusion, but for the wrong reasons. A vaccine which induces antibodies should prevent spread because it will prevent your body from producing large quantities of the virus and hence prevent viral shedding.

The remaining factors which still require masks are the non-perfect efficiency (~5% of people will still get it), social factors (related to creating two classes of people; the immune and non-immune) and perhaps some others I forgot.

[sokoloff]

While I think I agree with you high-level, you and GP may be talking past each other when you use “prevent” when you more precisely mean “dramatically reduce [possibly to the point where you effectively prevent]”.

[feanaro]

You're right. I also just found out about research (mentioned somewhere downthread) on differences between antibody expression in different tissue types (some IgA subtypes predominantly found in mucosa while other IgG types being dominantly systemic and/or in the lower respiratory system). The discussion there is on a whole other level of precision and points toward a mechanism which might indeed make it possible for vaccinated people to transmit the disease with some degree so it's not quite as clear cut as I presented it.

Though, intuitively, I'd still bet that vaccination will reduce viral shedding and the total load shedded, thus also reducing transmission.