Are there any side effects to 16 month dog having vet recommended jabs?

His had his first two jabs as a pup but vet is calling us back for more..Is this necessary, are there any negative side effects to this?

Usually 1st shots are a set. The side effects of not having your dog immunized are far greater than getting his shots. Most dogs won't have any negative reactions. If they do for some reason, you and the vet can work together to figure out the best solution. Once the initial stuff is done, they just need shots once yearly.A dog without his parvo shots is much more likely to catch this fatal disease than a dog who has had his shots for example.( I had to do this with one of my ferrets that's developed an allergy to one of her shots. Most vets I've met are happy to discuss the best option.)

He needs his yearly boosters now. No harm in them. it helps to protect them.