Related Experiment Videos
Varicella vaccine trials in healthy children. A summary of comparative and follow-up studies
Insights
The OKA vaccine strain demonstrated minimal clinical reactivity and high immunogenicity in children, offering protection against varicella for up to 48 months. The KMcC vaccine strain showed unacceptably high reactivity.
Area of Science:
- Virology
- Immunology
- Vaccinology
Background:
- Varicella zoster virus (VZV) infection poses a significant health risk.
- Development of safe and effective VZV vaccines is crucial for public health.
- Previous vaccine candidates have shown varying efficacy and safety profiles.
Purpose of the Study:
- To compare the clinical reactivity, immunogenicity, and long-term efficacy of two VZV vaccine strains, OKA and KMcC.
- To evaluate the persistence of immune responses and protection against varicella infection post-vaccination.
Main Methods:
- Ten comparative clinical trials involving 369 healthy, seronegative children.
- Administration of OKA and KMcC VZV vaccine strains.
- Assessment of clinical reactivity, immunogenicity (fluorescent antibody assay, lymphocyte proliferation), and protection against varicella over 48 months.
Main Results:
- The OKA vaccine strains exhibited minimal clinical reactivity.
- The KMcC passage-40 vaccine strain showed high clinical reactivity (32%).
- Both vaccine strains achieved high immunogenicity (93%-100%) with persistent antibody and lymphocyte responses for 9-48 months. Only five mild varicella cases occurred in seroconverted children after known exposures. No vaccine virus reactivation as zoster was observed.
Conclusions:
- The OKA vaccine strain is a safe and effective candidate for VZV vaccination in children.
- Long-term persistence of immune responses and protection against varicella infection were demonstrated.
- The KMcC vaccine strain's high reactivity limits its clinical utility.
Abstract:
Beginning in 1979, OKA and KMcC strains of varicella zoster virus (VZV) vaccine were administered to 369 healthy seronegative children in a sequence of ten comparative clinical trials. Postimmunization clinical reactivity was minimal with the OKA vaccines but was unacceptably high (32%) with the KMcC passage-40 vaccine. Ninety-three percent to 100% immunogenicity was noted by fluorescent antibody assay and in vitro lymphocyte proliferation to VZV antigens. Follow-up studies demonstrated persistence of antibody and in vitro lymphocyte proliferation responses and protection or modification of infection nine to 48 months after immunization. Only five episodes of mild varicella occurred in children in whom seroconversion had occurred. These episodes were noted after at least 281 known varicella exposures. Vaccine virus reactivation as zoster had not occurred in any child.