Y'know what - all those that think that fit, healthy 30-something's should get it first, cause 'working', why didn't you/don't you volunteer for a vaccine trial?
After all, you'd have had a 50/50 shot of being vaccinated before everybody else.
It's the right thing to do, to protect the most vulnerable first.
But if that's not acceptable to the whingers, here's the selfish reason you can live with - by stopping the cases where people are dying, needing ICU beds etc, we can also ease the restrictions needed to stop the disease spreading.
Vaccinate the 20% most likely to end up ill/in ICU - no need to worry about overwhelming the NHS and killing loads of people. Life goes back to (closer to) normal for everyone.
Alternately, vaccinate 20% of the 'workers', and nothing changes, because that's not nearly enough to stop it spreading, and all those vulnerable people are still there, ready to catch it.