Do You Have To Vaccinate All Hen Chickens That Are Chicken Coop Raised And If You Do What Do You Get. We Are Only Getting Laying Hens .?

I have 5 chickens and one rooster, and they are not vaccinated, I didnt know until after  I got them. I have read since that chickens need vaccinated, mine are really healthy and happy free range layers who are also my pets so I want to keep them healthy. How do I vaccinate them, do I take them to a vet or give them pills crushed or some other way.