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January 5, 1994

Risk of Serious Acute Neurological Illness After Immunization With Diphtheria-Tetanus-Pertussis Vaccine: A Population-Based Case-Control Study

JAMA. 1994;271(1):37-41. doi:10.1001/jama.1994.03510250053034

Objective.  —To evaluate the association between serious acute neurological illness and receipt of whole-cell pertussis vaccine, given as diphtheria-tetanus-pertussis (DTP) vaccine.

Design.  —Population-based case-control study.

Setting.  —Outpatient and inpatient hospital settings, physician practices, and the general population in Washington and Oregon states.

Subjects.  —A total of 424 confirmed cases of neurological illness were identified prospectively during a 12-month period by statewide active surveillance from the population of 218000 children 1 to 24 months of age living in Washington and Oregon (estimated 368 000 DTP immunizations given). Each case child was matched to two population control children by birth date (±5 days), gender, and county of birth. Written immunization records were used to determine whether illness occurred within 7 days of immunization in case children, or within 7 days of the same reference date in control children, thus qualifying as exposed.

Main Outcome Measures.  —Outpatient and inpatient cases of complex febrile seizures, seizures without fever, infantile spasms, and acute encephalitis/ encephalopathy confirmed by an expert panel masked to immunization history.

Results.  —The estimated odds ratio (OR) for onset of serious acute neurological illness within 7 days for young children exposed to DTP vaccine was 1.1 (95% confidence interval [Cl], 0.6 to 2.0). When the analysis was restricted to children with encephalopathy or complicated seizures and adjusted for factors possibly affecting vaccine administration, the OR was 3.6 (95% Cl, 0.8 to 15.2). Odds ratios for specific study diagnoses varied, but all Cls included 1. No elevated risk was observed for the largest group of illnesses studied, nonfebrile seizures (OR, 0.5; 95% Cl, 0.2 to 1.5).

Conclusions.  —This study did not find any statistically significant increased risk of onset of serious acute neurological illness in the 7 days after DTP vaccine exposure for young children.(JAMA. 1994;271:37-41)