Varicella vaccine: the American experience

Area of Science:

• Virology
• Immunology
• Pediatrics

Background:

• Chickenpox (varicella) is a common viral infection caused by the varicella-zoster virus (VZV).
• Live attenuated varicella vaccine is available for prevention.
• Effectiveness and immune response vary across different populations.

Purpose of the Study:

• To evaluate the safety and effectiveness of live attenuated varicella vaccine.
• To assess immune responses in healthy children, leukemic children, and adults.
• To investigate long-term antibody persistence and protection against VZV.

Main Methods:

• Administration of live attenuated varicella vaccine.
• Monitoring for adverse effects and protection against varicella.
• Assessing immune reactions to VZV.
• Differentiating vaccine-type and wild-type VZV using PCR and restriction endonuclease digestion.
• Measuring VZV antibodies via latex agglutination assay.

Main Results:

• The vaccine is safe and effective in healthy children, eliciting the best immune responses.
• Leukemic children experience mild-to-moderate adverse effects (50%) but achieve high protection.
• Adult vaccinees show lower protection (70%) compared to children.
• Breakthrough varicella infections in vaccinees are typically modified.
• Vaccination in leukemic children reduces zoster incidence compared to natural chickenpox.
• Antibodies to VZV are detectable in >90% of leukemic children 8-10 years post-vaccination.

Conclusions:

• Live attenuated varicella vaccine is a safe and effective preventive measure for chickenpox.
• The vaccine provides substantial protection in both healthy and leukemic children, with long-term antibody presence.
• Vaccination offers advantages in leukemic children, including reduced zoster risk and sustained immunity.