For any weanlings that I am showing (as weanlings) or any weanlings leaving for new homes (as weanlings) they get - Eastern/Western/Venz, Influenza, Tetnaus, Rhino and WNV and then a 3 week booster.
For any weanlings that I will NOT be showing as weanlings or that aren't going to new homes (as weanlings) then I opt not to give them vaccinations until FEB of their yearling year (when I do my show horses) as I think it helps build them build up their immune system themself some too. Never had any problems, never had any get sick ext......
This is really a question that you should discuss with your vet!
I have been reading and hearing that vaccinating your foals earlier than 6 months "may" cause the horse to build incomplete antibody levels as they are protected from the dam if the dam was vaccinated properly prior to the foal's birth.
I personally don't like to give vaccines earlier than 6 months, but then again I don't like to wean earlier than 5 to 6 months so our foals have enough protection from their dams.
Anyway, give your vet a call and verify what you should give your foal and when. Most vets are more than happy to answer this question! I also know that some of the vaccines when purchased seperately state different ages for the initial dosage. And remember, you want to give 2 shots of the same vaccine spaced approx 4 weeks apart to get complete protection.