PEDIATRICS Vol. 116 No. 6 December 2005, pp. 1613 (doi:10.1542/peds.2005-2258)
Eczema and Postvaccination Varicella Breakthrough
Mary Ann Goss, MSNPaul R. Beninger, MD
Clinical Risk Management and Safety Surveillance,
Merck & Co, Inc,
West Point, PA 19486
To the Editor.—
The authors of the article "Importance of Catch-up Vaccination: Experience From a Varicella Outbreak, Maine, 2002–2003" from the April 2005 issue of Pediatrics investigated the causes of a varicella outbreak in an elementary school, including vaccine failure.1 They noted that a history of eczema was associated with an increased risk for vaccine failure (relative risk: 4.3; 95% confidence interval: 0.8–23.5; N = 3), although there was not statistical significance and the numbers were small. They suggested that a poorer immune response caused by the disease itself or steroid therapy were plausible explanations. This prompted us to look at the Worldwide Adverse Experience System database,2 the company's repository for adverse-experience data, to conduct an analysis by using all the available data of cases of varicella breakthrough postvaccination in patients with the medical condition of eczema.
METHODS
Proportional reporting ratios (PRRs), an approach that uses quantitative methods to evaluate spontaneous reports for potential signals, were used for this analysis.3
A PRR was calculated by comparing the proportional reporting rate for reports that include a medical condition of eczema (N = 101) to the proportional reporting rate for reports that do not contain a medical condition of eczema (N = 17175).
RESULTS
A PRR was calculated as seen in Table 1.
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DISCUSSION
The expected, or null, value for a PRR is 1.0.3 The PRR of 1.15 indicates that the reporting ratios are similar and that there is not a statistically significant difference in the reporting rates between the 2 groups. Thus, an analysis that takes into account all the available reports supports the results of Marin et al, which indicate that there is no evidence of a statistically significant association between a medical history of eczema and an increased rate of breakthrough varicella postvaccination.
CONCLUSIONS
This analysis demonstrates that the reporting rate of breakthrough varicella in children with eczema is similar to that in children without eczema in their medical history. Although PRR is but one tool available for the assessment of postmarketing spontaneous reports, it may be a useful adjunct in the evaluation of a potential signal.
REFERENCES
- Marin M, Nguyen HQ, Keen J, et al. Importance of catch-up vaccination: experience from a varicella outbreak, Maine, 2002–2003.
Pediatrics. 2005;115
:900
–905
[Abstract/Free Full Text] - Lehman HP, Benson JO, Beninger PR, Anderson CA, Blumenthal SJ, Sharrar RG. A five-year evaluation of reports of overdose with indinavir sulfate. Pharmacoepidemiol Drug Saf. 2003;12 :449 –457[Medline]
- Evans SJ, Waller PC, Davis S. Use of proportional reporting ratios (PRRs) for signal generation from spontaneous adverse drug reaction reports. Pharmacoepidemiol Drug Saf. 2001;10 :483 –486[CrossRef][Web of Science][Medline]
PEDIATRICS (ISSN 1098-4275). ©2005 by the American Academy of Pediatrics
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