Immunogenicity of Oka/Merck varicella vaccine in children vaccinated at 12-14 months of age versus 15-23 months of age.

Abstract

OBJECTIVE:

Recent reports suggest that breakthrough varicella may be more common in children when the Oka/Merck varicella vaccine is given at 12-14 months of age than when it is given at older ages. An analysis of 5 postlicensure clinical trials with this vaccine was conducted to evaluate immune response relative to the age of the vaccine recipient.

METHODS:

In 5 clinical trials, 3771 children, 12 through 23 months of age with no history of varicella, received an injection of varicella vaccine. Varicella-zoster virus (VZV) antibody was measured 6 weeks postvaccination by glycoprotein enzyme-linked immunosorbent assay (gpELISA), an assay that correlates with neutralizing antibody. Endpoints evaluated were the response rate (percent of subjects with VZV antibody > or =5 gpELISA units/mL, a titer shown to correlate with protection) and geometric mean titer (GMT) of VZV antibody. Each endpoint was compared across 3 age groups (12-14, 15-17, and 18-23 months of age). Response rates by initial VZV serostatus were evaluated for children vaccinated at 12-14 months of age to assess whether maternal antibody had an impact on the immune response.

RESULTS:

The response rates were similar among 12-14, 15-17, and 18-23 month olds (93.8, 90.8, and 93.1%, respectively); GMTs were significantly higher among the 12-14 month olds (15.1, 13.5, and 13.7 gpELISA units/mL, respectively). Among children 12-14 months of age, response rates and GMTs were similar regardless of their prevaccination VZV serostatus.

CONCLUSIONS:

Oka/Merck varicella vaccine is highly immunogenic when given to children 12-14 months of age. The immunogenicity profile is similar to that of children 15-17 and 18-23 months of age. The presence of low titers of VZV antibody before vaccination did not influence vaccine response in 12-14 month olds. These results support current recommendations for universal varicella vaccination beginning at 12 months of age.

• Authors: Jeffrey L Silber, Ivan S F Chan, William W Wang, Holly Matthews, Barbara J Kuter
• Journal: The Pediatric infectious disease journal (Pediatr Infect Dis J) Vol. 26 Issue 7 Pg. 572-6 (Jul 2007) ISSN: 0891-3668 [Print] United States
• PMID: 17596796 (Publication Type: Journal Article, Meta-Analysis)

Chemical References

• Antibodies, Viral
• Chickenpox Vaccine

Topics

• Aging (immunology)
• Antibodies, Viral (blood, immunology)
• Chickenpox (immunology, prevention & control)
• Chickenpox Vaccine (administration & dosage, immunology)
• Drug Administration Schedule
• Herpesvirus 3, Human (immunology)
• Humans
• Infant