Most children who get the MMR vaccine experience no side effects or very mild ones, such as redness or soreness around the injection site and mild fever. However, a small percentage of recipients experience serious side effects, including high fever and seizures. There is also a small chance of an allergic reaction to the vaccine, according to MedlinePlus.
According to BabyCenter, one in five children develops a low-grade fever a few days after the injection. One in 20 develops a mild rash because of the injection. Most of these side effects occur within five to 14 days after the injection. Seizures affect one in 3,000 who take the shot, and one patient in 40,000 recipients develops a low platelet count.
According to MedlinePlus, MMR shots are a part of the series of recommended shots for children. Most must provide proof of the vaccination to enroll in school. Some parents are reluctant to vaccinate their child because of a study published in the British medical journal, "The Lancet," in 1998 linking the MMR vaccine to autism in children, according to BabyCenter. The findings of the study leading to this publication were determined to be coincidence, and the lead author was stripped of his medical and academic credentials.