Varicella Vaccine
General Characteristics
- Derived from live-attenuated Oka strain of varicella-zoster virus.
- Minimum 1000 plaque-forming units required per dose.
- Available as monovalent preparation or combined measles, mumps, rubella, and varicella formulations.
- Supplied as freeze-dried lyophilized powder requiring sterile diluent.
- Store vaccine and diluent strictly at 2-8°C.
- Protect from light and administer within 30 minutes of reconstitution.
- Administer 0.5 milliliter subcutaneously over anterolateral thigh or upper arm.
Immunization Schedule
- Indian Academy Of Pediatrics recommends universal vaccination for children.
- Minimum administration age is 12 months.
- Preferred initiation at 15 months to minimize breakthrough infection risk.
- Two-dose primary schedule recommended.
- First dose administered at 15-18 months.
- Second dose administered 3-6 months post-first dose.
- Catch-up vaccination (<13 years): Two doses spaced 3 months apart.
- Catch-up vaccination (>13 years): Two doses spaced 4-8 weeks apart.
- Post-exposure prophylaxis: Administer within 3-5 days of exposure for optimal efficacy.
Efficacy And Breakthrough Disease
- Breakthrough varicella occurs >42 days post-vaccination, typically 2-5 years later.
- Breakthrough clinical presentation remains mild, featuring <50 maculopapular lesions, minimal fever, and shorter illness duration.
- Two-dose schedules significantly reduce breakthrough incidence compared to single dose.
| Parameter | Single Dose | Two Doses |
|---|---|---|
| Seroconversion Rate | 86 percent | 99 percent |
| Efficacy Against Mild Disease | 70-90 percent | 98.3 percent |
| Efficacy Against Moderate/Severe Disease | >95 percent | 100 percent |
High-Risk Indications
- Chronic cardiac or pulmonary conditions.
- Asymptomatic HIV infection maintaining CD4 >15 percent.
- ALL in continuous remission >12 months, off chemotherapy, maintaining lymphocyte count >700/mm³ and platelet count >100,000/mm³.
- Children requiring prolonged salicylate therapy (salicylates must be withheld 6 weeks post-vaccination).
- Seronegative household contacts of immunocompromised individuals to prevent secondary transmission.
Contraindications And Precautions
- Severe anaphylaxis history to previous dose or vaccine components including gelatin or neomycin.
- Pregnancy (must avoid conception 4 weeks post-vaccination).
- Severe cellular immunodeficiency or symptomatic human immunodeficiency virus infection.
- Recent administration of antibody-containing blood products or intravenous immunoglobulin (mandates 5-11 month delay).
- Concurrent moderate-to-severe acute illness or thrombocytopenia.