What are the recommendations for Varicella (chickenpox) vaccination for individuals who have not had the disease or been previously vaccinated?

Varicella Vaccination Recommendations

All individuals without evidence of immunity to varicella should receive a two-dose vaccination series: children aged 12 months through 12 years receive doses at 12-15 months and 4-6 years (minimum 3-month interval), while adolescents and adults ≥13 years receive two doses 4-8 weeks apart. 1, 2

Evidence of Immunity

Before vaccination, assess for evidence of immunity, which includes: 1, 3

• Documentation of age-appropriate vaccination (two doses for most individuals)
• Laboratory confirmation of immunity or disease
• Birth in the United States before 1980 (except for healthcare personnel, pregnant women, and immunocompromised persons)
• Healthcare provider diagnosis or verification of varicella or herpes zoster

Standard Two-Dose Vaccination Schedule

Children (12 months through 12 years)

• First dose: 12-15 months of age 1, 2
• Second dose: 4-6 years of age (before school entry) 1, 2
• Minimum interval: 3 months between doses 1, 2
• Acceptable accelerated interval: 28 days (if second dose given inadvertently at 28 days to 3 months, do not repeat) 2
• Vaccine formulation: Single-antigen varicella vaccine (Varivax) or MMRV (ProQuad) for ages 12 months-12 years only 1, 2

Adolescents and Adults (≥13 years)

• Two doses: 4-8 weeks apart 1, 2
• Minimum interval: 4 weeks (28 days) 1, 2
• Vaccine formulation: Single-antigen varicella vaccine only (MMRV not licensed for this age group) 1, 2

Rationale for Two-Dose Regimen

The two-dose schedule provides superior protection compared to single-dose vaccination: 2

• 98% efficacy against any varicella disease vs. 94% with one dose
• 100% efficacy against severe disease
• Recipients are 3.3-fold less likely to develop breakthrough varicella
• >99% achieve protective antibody levels after two doses vs. 76-85% after one dose

Priority Groups Requiring Vaccination

Adults at increased risk who lack evidence of immunity should receive special consideration for two-dose vaccination: 1, 3

• Healthcare personnel (to prevent nosocomial transmission)
• Household contacts of immunocompromised persons
• Teachers and daycare employees
• College students, military personnel, and correctional facility staff
• Nonpregnant women of childbearing age
• International travelers

Catch-Up Vaccination

All individuals who previously received only one dose should receive a second dose: 1, 2

• Children <13 years: Minimum 3-month interval from first dose
• Persons ≥13 years: Minimum 4-week interval from first dose
• No need to restart series regardless of time elapsed since first dose 2

Contraindications

Varicella vaccine is contraindicated in: 1, 2

• Pregnancy (counsel to avoid conception for 1 month after each dose)
• Severe immunocompromising conditions (malignancy, primary immunodeficiency, AIDS with CD4 <200 cells/μL in adults or <15% in children)
• High-dose systemic corticosteroids (≥2 mg/kg/day or ≥20 mg/day prednisone for ≥14 days; wait ≥1 month after discontinuation before vaccinating) 1, 2
• History of anaphylactic reaction to vaccine components (gelatin or neomycin)

Important Clarifications on Contraindications

• Egg allergy is NOT a contraindication (vaccine contains no egg protein) 1, 2
• Contact dermatitis to neomycin is NOT a contraindication (only anaphylaxis is) 1
• Pregnant household member is NOT a contraindication for vaccinating other family members 2
• Breastfeeding is NOT a contraindication 1

Special Populations

Immunocompromised Persons

• Household contacts of immunocompromised persons should be vaccinated to provide indirect protection 1
• HIV-infected children may receive vaccine if CD4 ≥15% using two doses of single-antigen vaccine 3 months apart 2
• Leukemic children in remission should only be vaccinated with expert guidance and antiviral availability 1, 2
• Patients on low-dose steroids (<2 mg/kg/day or <20 mg/day prednisone) may be vaccinated 1

Pregnant Women

• Prenatal assessment for varicella immunity is recommended for all pregnant women 1
• Birth before 1980 is NOT considered evidence of immunity in pregnant women due to severe consequences of infection 1
• Postpartum vaccination: Administer first dose before hospital discharge if no evidence of immunity; second dose at 4-8 weeks (postpartum visit) 1

Healthcare Personnel

• All healthcare personnel without evidence of immunity must be vaccinated due to high risk of nosocomial transmission 1, 3
• Serologic screening before vaccination is cost-effective in this population 3
• Documented receipt of two doses supersedes subsequent serologic testing results 3

Post-Exposure Prophylaxis

For unvaccinated persons exposed to varicella: 1, 3

• Vaccinate within 3 days of exposure (>90% effective in preventing varicella)
• Vaccination up to 5 days post-exposure may still provide benefit (~70% effective in preventing disease, 100% effective in modifying severe disease)
• For high-risk persons with contraindications to vaccination: Administer VariZIG within 96 hours of exposure 1

School and Institutional Entry Requirements

• All children entering school should have received two doses or have other evidence of immunity 1, 2
• College students and other postsecondary educational institutions should enforce two-dose requirements 1
• During outbreaks: Unvaccinated persons without evidence of immunity should be excluded for 21 days after rash onset in last case 1

Common Pitfalls to Avoid

• Do not use MMRV vaccine in persons ≥13 years (not licensed for this age group) 1, 2
• Do not delay postpartum vaccination in women without evidence of immunity 1
• Do not withhold vaccine from household contacts of immunocompromised persons (benefits outweigh minimal transmission risk) 1
• Avoid salicylates for 6 weeks after vaccination due to Reye syndrome risk 2
• For first dose in children 12-47 months: Consider separate MMR and varicella vaccines rather than MMRV due to increased febrile seizure risk (one additional seizure per 2,300-2,600 doses) 2