Should a 13-Year-Old Receive a Second Dose of Varicella Vaccine?
Yes, a 13-year-old without evidence of varicella immunity should absolutely receive a second dose of varicella vaccine if they have only received one prior dose. 1
Vaccination Requirements for Adolescents Aged ≥13 Years
All persons aged ≥13 years without evidence of varicella immunity must receive two 0.5-mL doses of single-antigen varicella vaccine administered subcutaneously, 4-8 weeks apart. 1
Key Points for This Age Group:
The minimum interval between doses for persons aged ≥13 years is 4 weeks (not 3 months as in younger children). 1
Only single-antigen varicella vaccine may be used for vaccination of persons in this age group—MMRV is not licensed for use among persons aged ≥13 years. 1
If more than 8 weeks elapse after the first dose, the second dose may be administered without restarting the schedule. 1
Rationale for Second Dose in Adolescents
Enhanced Protection
Two-dose vaccination provides 98.3% effectiveness compared to one dose alone. 2
The odds of developing varicella are 95% lower for children who received 2 doses compared with 1 dose. 2
One dose of varicella vaccine does not provide sufficient herd immunity to prevent outbreaks in school settings, where exposure can be intense and transmission among vaccinated persons is effective. 3
Special Considerations for Adolescents
Adolescents are at higher risk for severe chickenpox and complications compared to younger children, including higher rates of pneumonia and disseminated disease. 4
All students should be assessed for varicella immunity, and those without evidence of immunity should routinely receive 2 doses of single-antigen varicella vaccine 4-8 weeks apart. 1
The risk for transmission of varicella among school-aged children, college students, and students in other postsecondary educational institutions can be high because of high contact rates. 1
Catch-Up Vaccination Protocol
Second dose catch-up varicella vaccination is specifically recommended for children, adolescents, and adults who previously received 1 dose. 1
The recommended minimum interval between the first dose and the catch-up second dose is 4 weeks for persons aged ≥13 years. 1
The catch-up second dose may be administered at any interval longer than the minimum recommended interval. 1
Catch-up vaccination may be implemented during routine health-care provider visits and through school- and college-entry requirements. 1
Clinical Evidence Supporting Two-Dose Regimen
Effectiveness Data
The incremental vaccine effectiveness of 2-dose vaccination was 79% in randomized controlled trials, 63% in cohort studies, and 81% in case-control studies. 5
In outbreak settings with 99% vaccination coverage, one-dose vaccination was not sufficient to prevent transmission, with vaccine effectiveness against varicella of any severity at 82% and 97% for moderate/severe varicella. 3
Immunogenicity
Two-dose vaccination resulted in significantly higher geometric mean titers and seroconversion rates compared to one dose. 5
99% of children receiving 2 doses achieved protective antibody levels compared with 86% of children who received 1 dose. 3
Common Pitfalls to Avoid
Do not delay the second dose beyond what is necessary—the minimum 4-week interval for adolescents aged ≥13 years should be respected, but longer intervals are acceptable. 1
Do not use MMRV vaccine in this age group—only single-antigen varicella vaccine is licensed for persons aged ≥13 years. 1
Do not assume that one dose provides adequate protection—breakthrough infections continue to occur and vaccinated persons with breakthrough disease remain contagious and able to sustain transmission. 3
Ensure proper documentation of vaccination dates—only doses with written documentation should be considered valid. 6
Implementation Strategy
The 11-12 year well-child visit should serve as an immunization visit to evaluate vaccination status and administer necessary vaccinations, including catch-up varicella vaccination for those who have received only one dose. 1
Physicians should use routine visits to ensure that all children without evidence of varicella immunity have received 2 doses of varicella vaccine. 1
From 2007 to 2014, varicella vaccination coverage with 2 or more doses increased from 8.3% to 66.9% in 13-15 year-olds, demonstrating successful implementation of catch-up campaigns, though missed vaccination opportunities persist. 7