Chickenpox vaccine not linked to strokes in children

Children who have received the chickenpox vaccine are not at risk of stroke or brain inflammation, according to researched published in the February 2009 issue of Pediatrics. Researchers note, "the existence and magnitude of any vaccine-associated risk has not been determined."

Lead author James G. Donahue, DVM, PhD, MPH, and colleagues analyzed data from 1991 to 2004 from the Vaccine Safety DataLink on 3.2 million children; 35.3% of the children had the varicella vaccine. The study identified 203 new stroke cases, 8 of which happened within 12 months of varicella vaccination. Of note, there was no clear linkage that the vaccination caused the strokes.

Researchers also detected 243 cases of brain inflammation or encephalitis. None of these cases took place in the first 30 days following vaccination. Further, no association was found between encephalitis and varicella vaccination during the 12 months post-vaccination.

"Complementing two recent reviews that found serious adverse events to be rare after varicella vaccination, this study offers reassurance that the rare complication of stroke seen after varicella infection" is simply a coincidence, not a cause and effect relationship, the team concludes.