Is a chickenpox (varicella) booster dose recommended for individuals who have previously received the varicella vaccine?

Varicella (Chickenpox) Booster Recommendations

A second dose of varicella vaccine is recommended for individuals who have previously received only one dose of the varicella vaccine, regardless of age, to provide optimal protection against chickenpox. 1, 2

Evidence-Based Rationale for Second Dose

The Advisory Committee on Immunization Practices (ACIP) recommends a two-dose varicella vaccination schedule for several important reasons:

• Enhanced Efficacy: Two-dose regimen provides significantly higher protection (98.3% efficacy) compared to a single dose (85% efficacy) 2
• Reduced Breakthrough Risk: The risk for breakthrough disease is 3.3-fold lower among children who received 2 doses compared to those who received only 1 dose 1
• Outbreak Prevention: Single-dose coverage, even when high (>90%), has been insufficient to prevent outbreaks in school settings 3

Recommendations by Age Group

Children (12 months to 12 years)

• If previously received only 1 dose: Administer second dose
• Optimal timing: Second dose at 4-6 years of age 2
• Minimum interval between doses: 3 months 1, 2

Adolescents and Adults (≥13 years)

• If previously received only 1 dose: Administer second dose
• Recommended interval between doses: 4-8 weeks 1, 2

Special Populations

Healthcare Personnel

• Healthcare workers with no evidence of immunity to varicella who previously received 1 dose should receive a second dose 1
• This is particularly important as healthcare workers are prioritized for vaccination due to their risk of exposure and transmission 2

Immunocompromised Individuals

• HIV-infected individuals with CD4 count ≥200 cells/μL who previously received 1 dose should consider completing the 2-dose series 1
• Severely immunocompromised patients: Varicella vaccine is contraindicated 1, 2

Post-Exposure Prophylaxis

For individuals with previous single-dose vaccination who are exposed to varicella:

• A second dose can be administered as post-exposure prophylaxis 4
• Highest effectiveness when given within 3 days of exposure (77% effective vs. 64% when given >3 days after exposure) 4

Important Clinical Considerations

• No Regular Boosters: Unlike some vaccines, varicella vaccination does not require regular boosters beyond the recommended two-dose series 2
• Breakthrough Disease: Breakthrough varicella after vaccination is typically milder with fewer lesions 1
• Primary vs. Secondary Vaccine Failure: Evidence suggests a relatively high rate of primary vaccine failure (no protective immunity after vaccination) rather than waning immunity, supporting the need for a second dose 5

Contraindications

• Pregnancy
• Severe immunocompromising conditions
• History of anaphylactic reaction to vaccine components 1, 2

Practical Implementation

When administering a second dose to someone who previously received one dose:

• No need for serologic testing before or after vaccination 2
• The second dose can be administered regardless of the time elapsed since the first dose 2
• If vaccination status is uncertain, administering a second dose is safe and recommended 1

The second dose of varicella vaccine not only provides individual protection but also contributes to community immunity, helping prevent outbreaks in school and other congregate settings.