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Background: It is unknown whether it is more cost-effective to test for varicella antibody or to immunize without testing in immigrant populations. The reliability of history of varicella disease is also unclear.Methods: The prevalences of varicella antibody in immigrant children from six regions of the world were used in a cost-effectiveness model to calculate the antibody prevalence above which it is more cost-effective to test rather than to immunize. History of varicella disease was obtained from chart review. We calculated the positive and negative predictive values of varicella history by age group and region.Results: The prevalence of varicella antibody above which it is more cost-effective to test than to immunize was 34% for children less than 13 years old and 17% for those aged 13 years and older. Overall, the positive predictive value of varicella history was 93-100% and the negative predictive value of varicella history was 28-66% among the six geographic regions.Conclusion: Immunization without serotesting was cost-effective in children <5 years of age. Testing prior to immunization was cost-effective in children 5 years of age and older. History of varicella was a good predictor of the presence of antibody to varicella, whereas a negative history was a poor predictor of the absence of antibody to varicella. [ABSTRACT FROM AUTHOR]

Hepatitis A is the most common vaccine-preventable disease in international travelers. Many individuals born and raised in hepatitis A endemic areas are likely to be immune to hepatitis A. Unnecessary hepatitis A immunization could be avoided by taking into account prior exposure to hepatitis A and judicious use of serotesting prior to immunization. Methods: Patients born and raised in countries of high prevalence of hepatitis A who were seen for pretravel consultation and who had hepatitis antibody measured were eligible. Data were collected about country of birth and length of residence there before emigration, length of time till departure on current trip, current age, and hepatitis A antibody result. Results: Patients ranged from 12 to 74 years of age and were from 27 countries. Their pretravel visit occurred from 4 to more than 90 days prior to departure. Ninety-five percent (122 of 129) of patients were immune to hepatitis A, including 100% (83 of 83) of those who resided in their country of origin until at least aged 20. Most patients were seen for pretravel consultation less than 28 days prior to departure. Conclusion: Individuals born and raised until aged 20 in hepatitis A endemic countries are likely to be immune to hepatitis A. Serotesting is most helpful in assessing immunity to hepatitis A in those under 20 years of age. [ABSTRACT FROM AUTHOR]