Aim: Acute cerebellar ataxia (ACA, sudden onset of truncal ataxia and gait disturbances) usually follows a benign illness (25% varicella). It is also described after vaccination, like MMR and varicella zoster virus (VZV). We will establish incidence rates of (varicella related) ACA and assess the attributable risk of vaccination to ACA in the Netherlands.
Method: Data on ACA in children, following infections, like varicella, and vaccinations, obtained from prospective, active pediatric surveillance and passive surveillance on adverse events following immunizations (AEFI) were compared with hospitalization data for ataxia. Capture-recapture (CRC) method was used to estimate the burden of ACA in the Netherlands.
Results: 45 children with ACA were included (44 and 1 reported by pediatric and AEFI surveillance respectively, 30 were hospitalized). Chickenpox preceded ACA in 15 cases, one case followed MMR. Of the hospitalization reports, 13 fulfilled the criteria for ACA. Using CRC the estimated number of hospitalized ACA cases was 42. For varicella related ACA, this estimate was 10, resulting in an incidence rate of 0.7:100,000 (95%CI 0.52-0.94, all cases) and 0.17:100,000 (95%CI 0.09-0.31, varicella related cases) for children under 15 years of age.
Conclusion: The incidence rates were comparable with other studies. We found no association with MMR, but chickenpox was clearly related to ACA. According to age-specific seroprevalence data the incidence rate of ACA was 5:100,000 VZV infections for children up to 5 years, compared to an ACA-reporting rate of 0.15:100,000 doses VZV-vaccine. Therefore, uptake of VZV-vaccine in the immunization programme will diminish the incidence rate of ACA.