The risk of seizures following MMR or MR immunization is evaluated in a retrospective cohort study conducted among 18,364 Tennessee children from The Department of Preventive Medicine, Vanderbilt University School of Medicine, Nashville, TN. Of 100 children (0.5%) with a confirmed seizure between the first MMR or MR and age 36 months, 77 had febrile seizures, 15 afebrile seizures and 8 acute symptomatic seizures. The incidence of febrile seizures was 4.3, 5.1, and 2.8 per 1,000 person-years in the 3 age groups, 361-540, 541-720, and 721-1,080 days, respectively. 4 children had febrile seizures in the 7-14 days following MMR or MR immunization, compared with 72 in the interval 30 or more days following MMR or MR with a relative risk of 2.1. The authors concluded that the increase in febrile seizures in the 7-14 day interval following MMR was coincident with the occurrence of fever post-immunization. [1]

COMMENT. This review of seizure occurrence was confined to those patients seen at a hospital and would not include seizures treated at home or at outpatient facilities. The authors admit that the ascertainment of seizures was incomplete but would include more serious seizures or neurologic events.

Measles was the cause of fever in 1.2% of 7,000 cases of febrile seizures reported in the world literature between 1929 and 1964. [2]