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By
Gene Emery
BOSTON (Reuters) -
Vaccinations pose only a small risk of causing fever-related seizures in
babies and the benefits of the shots far outweigh any risks, according to a
study of nearly 680,000 children in Thursday's New England Journal of
Medicine.
Even when seizures occur, the
researchers also found, the effect is only temporary.
Dr. William E. Barlow of the
Center for Health Studies in Seattle and his colleagues collected data from
four large health maintenance organizations which treat about one in 40
U.S. children under the age of 7 to see how many had seizures after being
vaccinated.
Compared to children who were
not recently vaccinated, the researchers found that fewer than 1 in 13,000
children protected against diphtheria, tetanus and whooping cough by the
DTP vaccine had a seizure. The seizure rate was less than 1 in 3,300 for
children who received the MMR vaccine for measles, mumps and rubella.
The seizures associated with
the MMR vaccinations tended to occur eight to 14 days after vaccination;
the DTP shot was most likely to spark a seizure on the day of the
vaccination. (An even safer version of the DTP vaccine has since come into
widespread use.)
When they followed the cases
of children who had a seizure, the Barlow team found that the risk of
having learning or developmental disabilities "did not differ between
children who had been exposed and those who had not been exposed" to
the vaccines at the time of their seizure.
In addition, they concluded,
children who had a seizure after a vaccination did not face a greater risk
of having future seizures, or of being diagnosed with epilepsy.
"A child's fever-related
seizure did not result in any lasting adverse consequences for the
child," Barlow said.
The benefits of the shots
outweigh the risks, they said. For example, unvaccinated children risk
neurological problems if they develop measles or whooping cough.
The MMR vaccine is usually
given at age 12 months to 15 months, with a booster between the ages of 4
and 6. At the times of the study, the DTP vaccine was given in five doses
from ages 2 months to 6 years.
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