id talk to the vet about "shoulds". as there isnt gonna be any one correct answer. It depends on your horse, where you ride, where you gonna take him, wheres he gonna drink, how much risk you are willing to assume, etc etc.
Id check CO websight for actual legally must haves, but talk to the vet about the others, sorta why I pay them to know things like that. My endurance horse that travels up and down the east coasts is mixed in and around strange horses constantly, drinks from community water troughs a hundred other horses drank from that day gets way differnt vacines than an old retired guy that doesnt leave the property.