Yes, You Need a Second Dose of Varicella Vaccine
If you received only one 0.5mL dose of varicella vaccine, you absolutely need a second dose to achieve optimal protection against chickenpox. The standard recommendation is a two-dose series for all individuals, regardless of age 1.
Timing for Your Second Dose
The timing depends on your age:
If You Are 12 Months Through 12 Years Old
- Minimum interval: 3 months between doses 1, 2
- The second dose is ideally given at age 4-6 years (before school entry), but can be administered earlier as long as 3 months have passed 1, 2
- Important exception: If the second dose was accidentally given between 28 days and 3 months after the first dose, it still counts as valid and does not need to be repeated 1, 2
If You Are 13 Years or Older
- Minimum interval: 4 weeks (28 days) between doses 1, 3
- The recommended interval is 4-8 weeks, though longer intervals are acceptable 1, 3
- Only single-antigen varicella vaccine (not MMRV) can be used in this age group 1, 3
Why Two Doses Matter
The evidence strongly supports two-dose vaccination:
- One dose effectiveness: 81-84.5% against all varicella, 98-100% against moderate/severe disease 4, 5
- Two dose effectiveness: 92-98.3% against all varicella, 99.1% against moderate/severe disease 6, 4
- Risk reduction: Recipients of two doses are 3.3-fold less likely to develop breakthrough varicella compared to one-dose recipients 1, 2
- After two doses, >99% of children achieve protective antibody levels, compared to only 76-85% after a single dose 2
Catch-Up Vaccination Protocol
You should receive your second dose as soon as the minimum interval has passed 1, 3:
- Schedule your second dose now if you are past the minimum interval for your age group 1, 3
- There is no maximum interval—the series does not need to be restarted regardless of how much time has elapsed 2
- Catch-up vaccination is specifically recommended for all children, adolescents, and adults who previously received only one dose 1, 3
Common Pitfalls to Avoid
- Don't assume one dose is sufficient: While one dose provides good protection against severe disease, it leaves you vulnerable to breakthrough infections, especially in high-transmission settings like schools 1, 2
- Don't use MMRV vaccine if you're 13 or older: Only single-antigen varicella vaccine is licensed for persons ≥13 years 1, 3
- Don't delay unnecessarily: The second dose should be administered as soon as the minimum interval is met, particularly for school-aged children and adolescents who face higher transmission risk 1