NEW YORK (Reuters Health) – Unlike chickenpox itself, the vaccine against chickenpox does not increase the risk of stroke or brain inflammation in children, according to a large US study reported in the journal Pediatrics.
Stroke is a known complication of chickenpox, a viral disease also called varicella, the study team points out. Although there have been case reports of stroke after varicella vaccination, "the existence and magnitude of any vaccine-associated risk has not been determined."
To shed light on this subject, Dr. James G. Donahue of the Marshfield Clinic Research Foundation, Wisconsin and colleagues analyzed data for the period 1991 through 2004 from the Vaccine Safety DataLink on 3.2 million children, 35.3 percent of whom received the varicella vaccine.
They identified a total of 203 new stroke cases, including 8 that occurred within 12 months of varicella vaccination. However, the timing of each case did not suggest that vaccination caused the strokes.
Stroke was strongly associated with known risk factors such as sickle cell disease and heart disease, they found.
Donahue and colleagues also identified 243 cases of brain inflammation or encephalitis. None of these cases occurred during the first 30 days after vaccination and there was no association between encephalitis and varicella vaccination at any time in the 12 months after 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.
SOURCE: Pediatrics, February 2009.
Copyright © 2009 Reuters Limited.
I don't believe it. If there is a known correlation between stroke and chicken pox, then it has to be the same with a vaccine. The body often can't tell the difference and doesn't care about the delivery method of the virus. Wild strain or vaccine strain, if that's how the body can respond then there IS a relationship. I wonder how much money went into this study compared to the potential law suit money people may have gotten.