Varicella (Chickenpox) Vaccine

Varicella, commonly known as chickenpox, is an acute, highly contagious infectious disease caused by the Varicella-Zoster Virus (VZV). It typically presents with a characteristic pruritic (itchy) vesicular rash, fever, and malaise. Although often perceived as a benign childhood illness, varicella can cause severe, life-threatening complications, including secondary bacterial skin infections (such as group A streptococcal sepsis), viral pneumonia, encephalitis, and cerebellar ataxia. Furthermore, following primary infection, the virus remains latent in sensory nerve ganglia and can reactivate decades later as herpes zoster (shingles).

Prior to the introduction of widespread immunization programs, varicella was nearly universal, causing millions of cases annually worldwide. In jurisdictions with high vaccine coverage, such as those adhering to CDC and ECDC guidelines, routine childhood varicella vaccination has successfully reduced chickenpox cases, hospitalizations, and deaths by over 95%. However, varicella remains endemic in countries without universal childhood vaccination mandates, representing a persistent public health burden.

• Schedule: Typically administered as a live-attenuated virus vaccine in a two-dose series. Public health guidelines recommend the first dose at 12 to 15 months of age and the second booster dose at 4 to 6 years of age. Catch-up schedules are available for adolescents and adults who lack evidence of immunity.
• Eligibility: Indicated for healthy children 12 months or older and susceptible adolescents/adults.
• Contraindications: Because it is a live virus vaccine, it is generally contraindicated in pregnant individuals, persons with severe immunodeficiency (e.g., advanced HIV or those undergoing immunosuppressive oncological therapies), and individuals with a history of anaphylaxis to neomycin or gelatin.
• Safety Profile: Clinical surveillance data indicate that the vaccine is highly safe. Common side effects include mild injection-site pain, swelling, low-grade pyrexia, and occasionally a mild, localized maculopapular or vesicular rash near the injection site.
• Efficacy Data: Clinical trials and real-world evidence confirm that two doses of the varicella vaccine provide approximately 98% protection against any form of varicella infection and virtually 100% protection against severe disease and death.

Achieving high population vaccination coverage is essential to establish herd immunity (indirect protection that occurs when a large percentage of a population becomes immune, making disease spread unlikely). This helps safeguard vulnerable individuals who cannot be medically vaccinated, such as newborns and severely immunocompromised patients. Susceptible adults who contract varicella face a significantly higher risk of severe systemic complications compared to young children, making catch-up screening and vaccination essential for non-immune adults.