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J Infect Dis. 2011 Feb 1;203(3):312-5. doi: 10.1093/infdis/jiq052.

Effectiveness of 2 doses of varicella vaccine in children.

Author information

1
Department of Pediatrics, Yale University School of Medicine and Graduate School of Arts and Sciences, New Haven, Connecticut 06520-8064, USA. eugene.shapiro@yale.edu

Abstract

BACKGROUND:

Because of ongoing outbreaks of varicella, a second dose of varicella vaccine was added to the routine immunization schedule for children in June 2006 by the Centers for Disease Control and Prevention.

METHODS:

We assessed the effectiveness of 2 doses of varicella vaccine in a case-control study by identifying children ≥4 years of age with varicella confirmed by polymerase chain reaction assay and up to 2 controls matched by age and pediatric practice. Effectiveness was calculated using exact conditional logistic regression.

RESULTS:

From July 2006 to January 2010, of the 71 case subjects and 140 matched controls enrolled, no cases (0%) vs 22 controls (15.7%) had received 2 doses of varicella vaccine, 66 cases (93.0%) vs 117 controls (83.6%) had received 1 dose, and 5 cases (7.0%) vs 1 control (0.7%) did not receive varicella vaccine (P < .001). The effectiveness of 2 doses of the vaccine was 98.3% (95% confidence level [CI]: 83.5%-100%; P < .001). The matched odds ratio for 2 doses vs 1 dose of the vaccine was 0.053 (95% CI: 0.002-0.320; P < .001).

CONCLUSION:

The effectiveness of 2 doses of varicella vaccine in the first 2.5 years after recommendation of a routine second dose of the vaccine for children is excellent. Odds of developing varicella were 95% lower for children who received 2 doses compared with 1 dose of varicella vaccine.

Comment in

PMID:
21208922
PMCID:
PMC3071110
DOI:
10.1093/infdis/jiq052
[Indexed for MEDLINE]
Free PMC Article

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