High risk situations would be foals, horses that will be at breeding facilities, horses that travel and are exposed to large groups of new horses regularly and during times of stress (shows/competitions) etc. You should also consider that even horses in these situations may not need vaccination if they have had strangles in the last 5 years because 75% of horses develop a strong, long-lasting immunity after recovery from the disease.
Horses are not more at risk in the weeks following vaccination. Vaccination provides protection in 1-2 weeks in horses who are getting boosters but for foals or first time vaccinates you should consider that they are not fully protected until after the full initial series is given.
Licensed Veterinary Technician