Originally Posted by nomadking

It DOESN'T give you immediate protection from the real thing. You could STILL pick that up around the time of vaccination or even afterwards.
You will NOT be able to get the vaccine and then immediately go out and about as if there was no problem at all. Even once the immune system is all prepared for the real thing, it STILL takes time for the immune system to deal with it, although it is quicker in doing it.

In some ways the priorities might be the wrong way around. Vaccinate those most like to spread it around, eg the young, keep them in lockdown for a further 2 weeks. It then should be safer out there for the rest of us to go out and be vaccinated. Having the young face a further 4 weeks in lockdown even with a vaccine, isn't going to work.