All horses not previously vaccinated should be vaccinated twice with 4-6 weeks interval, followed by a third vaccination 5-7 months later.
Foals should ideally be vaccinated at about 6 months of age.
According to vets: first jab gets usually done around 6 months of age. Then 2nd jab gets done between 21-92 days after the first. Then 3rd jab gets done 150-215 days after the 2nd jab. And then yearly. Hope that helps.