Second Dose of Varicella Vaccine May Be Needed to Prevent School Outbreaks

georgia · medicine forum Guru Joined: 06 May 2005 Posts: 505

http://www.medscape.com/viewarticle/536566
Medscape

Second Dose of Varicella Vaccine May Be Needed to Prevent School
Outbreaks

NEW YORK (Reuters Health) Jun 16 - One dose of varicella vaccine may be
insufficient to prevent school outbreaks of chickenpox, according to a
report in the June issue of Pediatrics.

Outbreaks of varicella continue to be reported, even in highly
vaccinated
populations, the authors explain.

In Arkansas, a varicella vaccination requirement for entry into
kindergarten
was introduced in 2000, so by September 2003 children in kindergarten
through third grade 3 were covered. Nonetheless, a large number of
cases of
chickenpox occurred in an elementary school in 2003. Dr. Sandra L. Snow
from
the Arkansas Department of Health, Little Rock, and colleagues
investigated
the outbreak.

Among the 545 children attending the school, 96% who had a negative
disease
history had been vaccinated, the team found, including 14 children who
had
received two doses of varicella vaccine.

Forty-three of 48 students (90%) who developed varicella had been
vaccinated, the findings indicate, and the highest attack rate occurred
in a
first grade classroom where all of the students had been vaccinated.

Most of the vaccinated patients had mild disease, the researchers note,
with
only 6% appearing sick and only a median two days of school being
missed.

The overall vaccine effectiveness was 82% for varicella of any severity
and
97% for moderate or severe varicella, the report indicates.

None of the previously reported risk factors for varicella in
vaccinated
persons were statistically significant in this study.

"The effectiveness of 1 dose of varicella vaccine is not adequate to
provide
sufficient herd immunity levels to prevent outbreaks in school settings
where exposure can be intense," the investigators conclude.

"Although the current recommendation of providing a second dose of
varicella
vaccine during an outbreak offers a possible tool for controlling
outbreaks,
a routine 2-dose recommendation would be more effective at preventing
cases," Dr. Snow and colleagues add. "Routine 2-dose vaccination will
provide improved protection against disease and further reduce
morbidity and
mortality from varicella."

Pediatrics 2006;117:e1070-e1077.

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