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Contrary to widely held beliefs, most
10-year-old children with negative or unknown varicella (chickenpox)
histories are actually immune to chickenpox.
Investigators from Laval University in
Quebec assessed the age-specific incidence of chickenpox in
over 2000 fourth grade students. A subset of children with
negative or unknown chickenpox histories were tested for anti-varicella
antibodies.
The study was performed to determine the
proportion of children that would need to be vaccinated in
a catch-up program.
The reported cumulative incidence of chickenpox
at 10 years of age was 92%. Furthermore, about half of the
children developed chickenpox before entering kindergarten.
Of the children
with negative or unknown chickenpox histories, 63% had antibodies
against the virus.
Prevaccination testing could identify
children who are immune, but such testing could be difficult
to implement and might reduce vaccine coverage.
Pediatric
Infectious Disease Journal November 2001;20:1087-1088
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