Primary versus secondary failure after varicella vaccination: implications for interval between 2 doses.

BACKGROUND Two-dose varicella vaccination is recommended for optimal control of varicella in populations with high (>90%) 1-dose coverage. Optimal timing of the second dose may depend on whether breakthrough varicella results from primary vaccine failure (no protective immunity after vaccination) or secondary vaccine failure (waning protective immunity). METHODS Published literature (1995 to 2012) on vaccine failure after varicella vaccination cited in PubMed and other online sources was reviewed. RESULTS Nineteen publications detailed 21 varicella outbreaks with breakthrough varicella rates ranging from 0% to 42%; the publications showed no consistent trend between breakthrough varicella rate and time since vaccination. CONCLUSIONS Literature to date indicates a relatively high rate of primary vaccine failure and limited evidence of secondary vaccine failure among 1-dose varicella vaccine recipients, suggesting that a short interval between 2 doses might be preferable in countries considering implementation of universal varicella vaccination to reduce breakthrough varicella. However, any potential disruption to well-established vaccination schedules should be considered.