Childhood vaccination is linked with earlier onset of the neurological disorder Dravet syndrome, finds a retrospective study. But vaccination should not be withheld from children with Dravet syndrome because vaccination before or after disease onset does not affect their clinical outlook, concludes the Article published Online First and in the June edition of The Lancet Neurology.
Proposed links between childhood vaccination and neurological disorders have repeatedly caused controversy and have affected vaccination uptake. Pertussis vaccine, which is routinely given to children together with diphtheria and typhoid vaccines (DTP), has been linked in the past with vaccine encephalopathy – in which seizures and intellectual disability develop. An Australia-wide team led by Samuel Berkovic of the Epilepsy Research Centre at the University of Melbourne reported in The Lancet Neurology in 2006 that 12 of 14 patients with so-called vaccine encephalopathy subsequently were found to have Dravet syndrome, which was associated with mutations of the sodium channel gene SCN1A in 11 of the 12 affected children.
To confirm the association between DTP vaccination and Dravet syndrome and determine whether vaccination affects time of onset or clinical outcome of the disorder, Anne McIntosh and Jacinta McMahon (Epilepsy Research Centre, University of Melbourne, Victoria) and colleagues, led by Berkovic and Ingrid Scheffer, retrospectively studied 40 patients with Dravet syndrome. The cohort was selected because they had mutations in SCN1A, a first seizure that was a convulsion, and validated medical and vaccination records, and not because of any temporal link of seizures with vaccination.
The team found a peak in the number of patients who had seizure onset within 2 days of vaccination. So the authors separated the children into two groups according to whether seizure onset occurred on the day or day after vaccination (vaccination-proximate group, n=12) or not (vaccination-distant group, n=28).
The average age at seizure onset was significantly lower in the vaccination-proximate group (18•4 weeks) compared with the vaccination-distant group (26.2 weeks). There were no differences in intellectual outcome, subsequent seizure type, or gene mutation type between the two groups. A further analysis found that intellectual outcome did not differ between patients who received vaccinations after seizure onset and those who did not.
Universal vaccination in infancy is an emotive issue, in which science, societal views, and social policy are sometimes poorly aligned", say the authors, paraphrasing a recent authoritative review by Professors Simon Shorvon (UK) and Anne Berg (USA). The Article authors liken the attention given to the previous debate over pertussis vaccination and so-called vaccine encephalopathy to that given recently to the debate over MMR vaccine and autism.
"Vaccination might trigger earlier onset of Dravet syndrome in children who, because of an SCN1A mutation, are destined to develop the disease", the authors note. "However, vaccination should not be withheld from children with SCN1A mutations because we found no evidence that vaccinations before or after disease onset affect outcome."
In a Comment, Max Wiznitzer from the Rainbow Babies & Children's Hospital in Cleveland notes that the study is "consistent with the conclusion that outcome is determined by the underlying disorder and not by proximity to vaccine administration". Moreover, he urges: "Through effective and accurate information and communication about benefits and realistic risks, public confidence in vaccines can be strengthened."
Journal
The Lancet Neurology