Varicella: efficacy of two-dose vaccination in childhood.

INTRODUCTION: Experience with one-dose varicella vaccination of children in the USA has shown that with high immunization coverage a marked decline in morbidity and mortality occurs. However, about one quarter of the vaccinees may develop breakthrough varicella. Although breakthrough infections are usually mild, the patients are potentially contagious.

METHODS: Selective literature search, review of congress papers, and evaluation of the consensus statement of an expert panel on the use of monovalent varicella vaccines.

RESULTS: Recent studies on the causes, effects, and consequences of breakthrough varicella after one-dose vaccination show that varicella vaccine should be given in two doses at least four to six weeks apart to achieve effective, long-lasting protection against chickenpox. Breakthrough disease cannot always be prevented, but two-dose vaccination offers significantly better protection than a single dose. These findings were considered in the approval process for the measles-mumps-rubella-varicella combination vaccines, which are licensed only for use in a two-dose schedule.

DISCUSSION: The authors recommend the general implementation of a two-dose schedule for single-antigen varicella vaccines, which will continue to be available.