Immunization Science

Are two doses of varicella vaccine more effective?

The article

Ten year follow-up of healthy children who received one or two injections of varicella vaccine. Kuter B, Matthews H, Shinefield H, Black S, Dennehy P, Watson B, Reisinger K, Kim LL, Lupinacci L, Hartzel J, Chan I, and The Study Group For Varivax. The Pediatric Infectious Disease Journal 2004;23(2):132-137

varicella (chickenpox) vaccine more effective against chickenpox than one dose of the vaccine?

The study

This study included a total of 2,216 children 12 months to 12 years of age with a negative history of varicella; 1,114 received 1 injection of varicella vaccine, and 1,102 received 2 injections. The two injections were given 3 months apart from each other.

The researchers followed the children for varicella, any varicella-like illness or zoster (shingles) and any exposures to varicella or zoster on a yearly basis for 10 years after vaccination. They also measured yearly the persistence of varicella antibody for 9 years.

The findings

A total of 60 children who received 1 injection and 17 who received 2 injections of vaccine had a breakthrough case of varicella (usually mild chickenpox in vaccinated persons). Among the children who developed a breakthrough case of varicella, the majority had mild disease (less than 50 lesions).

In both groups most breakthrough cases occurred between Years 2 and 5 after vaccination. There were no breakthrough cases of varicella in Years 7 to 10 in the recipients of two injections, but cases continued to occur in recipients of one injection during those years.

Both the one and two dose regimens protected all children from having more than 300 lesions and fever of 102