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Vaccine. 2012 Jul 20;30(34):5094-8. doi: 10.1016/j.vaccine.2012.05.072. Epub 2012 Jun 9.

A varicella outbreak in a school with high one-dose vaccination coverage, Beijing, China.

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1
Beijing Center for Disease Control and Prevention, Beijing, PR China.

Abstract

BACKGROUND:

Varicella vaccine is available in the private sector in China, with a single dose currently recommended for children aged ≥12 months. We investigated a varicella outbreak in a school in Beijing with high varicella vaccination coverage to describe the outbreak, examine risk factors for vaccine failure, and calculate vaccine effectiveness.

METHODS:

A varicella case was defined as an acute generalized maculopapular rash without other apparent cause in a student without prior varicella attending the elementary school during August 30-December 28, 2010. Varicella among vaccinated students (breakthrough varicella) was defined as varicella occurring >42 days after vaccination. Students' vaccination status was verified with immunization records and clinical presentations were collected from health care practitioners.

RESULTS:

Of the 951 students, 934 (98%) had no prior varicella history. Among these students, 916 had received 1 dose of varicella vaccine and 2 had received 2 doses (98% vaccination coverage) before the outbreak. A total of 87 cases occurred during the outbreak; most had breakthrough varicella (86/87, 99%) and mild disease (83/87, 95%). Age at vaccination (<15 months vs. ≥15 months) and time since vaccination before outbreak (<5 years vs. ≥5 years) were not associated with development of breakthrough varicella. Single-dose varicella vaccination was 89% effective in preventing any varicella and 99% in preventing moderate/severe varicella.

CONCLUSION:

Single-dose varicella vaccination is highly effective in reducing varicella incidence and mitigating disease severity, but not high enough to prevent outbreak. A two-dose program might help to prevent varicella outbreaks in Beijing.

PMID:
22687763
PMCID:
PMC4620431
DOI:
10.1016/j.vaccine.2012.05.072
[Indexed for MEDLINE]
Free PMC Article
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