My dog had a seizure will it happen again?

My mini pin is about 6 or 7 years old and i just took her to the vet to get her first vaccinations of her life. They give her three different ones and her heartworm. Two days after she had what seemed to be seizure. Should i be worried that this going to happen all the time now or could this a be one and done thing. I was also wondering if i should have even got her vaccinated.