Humoral and cell-mediated immune responses in healthy children after one or two doses of varicella vaccine.

This study compared the immune responses of healthy children to one or two doses of Oka/Merck varicella vaccine. Both cell-mediated and humoral immune responses were significantly stronger 1 year later among children given two doses 3 months apart than among those given a single dose. Long-term follow-up studies are needed to determine whether two doses of vaccine indeed provide more complete and more durable protection than a single dose against breakthrough varicella in healthy children.