What side effects are associated with the mmr vaccine?

Fever, rash: 5 to 15% of children may get a fever usually 6 to 12 days after the vaccine which usually lasts 1 to 2 days. A rash may develop in 5% of recipients. Children predisposed to febrile seizures may be at a slightly increased risk for a seizure. Allergic reactions may occur to neomycin, gelatin or rarely egg.

Fever mainly: Measles vaccine occasionally causes side effects in kids who don't have underlying health problems. The most common reactions are fever between 6-12 days after vaccination (in about 5%-15% of kids getting the vaccine) and a measles-like rash, which isn't contagious and fades on its own (in about about 5% of vaccinated kids). Children may also have local swelling ad reddness.