When should I vaccinate and what to treat for sneezing

[Koekoek]

Hi
I'm new to keeping chickens and recently started my flock.
On the welcome page Aracauna16 advised about vaccinating against Mareks disease.
When can I do this and is there anything else I should be vaccinating against?
I recently added 2 Potchefstroem Koekoek's to my flock and noticed that on the first day of me introducing them that they were sneezing, one not so bad, the other about once every minute.
Since then it seems to have improved quite a bit - they still sneeze but the intervals between each sneeze are much longer.
It has not as yet spread to any of the others.
Unfortunately only now am I thinking that I should have had a quarantine procedure in place.
Do you think I need to treat the sneezing with
medication and also should I adopt a quarantine procedure for future introductions to my flock?

 

[Koekoek]

Sorry also forgot to mention that I have 6 Leghorn chicks a few days old, what should I vaccinate them against and when?
I breed finches and have thousands of rands worth of them as well as some rare ones -so I want to be careful, the last thing I want is any diseases transferring to them from my chickens - a lot are so small and fragile, it could end in disaster.