Evaluation of live attenuated varicella vaccine (Oka-RIT strain) and combined varicella and MMR vaccination in 13-17-month-old children

Abstract

The Oka-RIT strain of live attenuated varicella vaccine at dose levels 5300 PFU (high titre) and 2000 PFU (low titre) was tested in 13-17-month-old children; 50% of the children received the varicella vaccine alone, and the other 50% received it together with a measles-mumps-rubella (MMR) vaccine. The high titre and low titre varicella vaccines induced 96% and 92% seroconversion rates, respectively. Following combined vaccination with MMR, the corresponding seroconversion rates for varicella were significantly lower at 85% and 72% respectively. Seroconversion rates to measles, mumps and rubella were not affected by the combination of varicella vaccine plus MMR vaccination. Single varicella vaccine at both titre levels was found safe, although 10% of the children had minor skin reactions, possibly attributable to the vaccine. Reactions typically associated with MMR vaccination did not significantly increase after the combined varicella plus MMR vaccination. This study confirmed that the Oka-RIT strain varicella vaccine is safe and immunogenic in healthy young children, but failed to find a totally satisfactory combination for a varicella-MMR vaccine.