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.