No, One Dose of Varicella Vaccine Plus Zoster Vaccine Does Not Provide Adequate Immunity to Chickenpox
You need a second dose of varicella vaccine specifically—not a zoster vaccine—to achieve adequate immunity against chickenpox. The zoster vaccines (Zostavax or Shingrix) are designed to prevent shingles (herpes zoster) in adults who have already had chickenpox or been fully vaccinated against it, not to provide primary immunity against chickenpox itself.
Why This Matters
The Varicella Vaccine Requires Two Doses for Optimal Protection
Current guidelines clearly establish that two doses of varicella vaccine are necessary to achieve evidence of immunity 1. Here's what the evidence shows:
- One dose effectiveness: 80-85% against any varicella disease, 94% over 10 years 1, 2
- Two dose effectiveness: 98% against any varicella disease, 100% against severe disease 1, 2
- Breakthrough risk: Recipients of one dose are 3.3-fold more likely to develop breakthrough varicella compared to two-dose recipients (7.3% vs 2.2%) 1, 2
The shift to a two-dose strategy occurred specifically because one dose left too many people susceptible, leading to continued outbreaks even in highly vaccinated populations 1, 3.
Zoster Vaccines Are Not Interchangeable with Varicella Vaccines
Shingrix (the recombinant zoster vaccine) is explicitly NOT indicated for prevention of primary varicella infection (chickenpox) 4. This is a critical distinction:
- Shingrix contains only the varicella-zoster virus glycoprotein E (gE) subunit with adjuvant—it's designed to boost cell-mediated immunity in people who already have immunity to VZV 4, 5
- Zostavax is a live attenuated vaccine with higher viral load than varicella vaccine, intended for adults ≥50-60 years who already have VZV immunity 6, 5
- Neither zoster vaccine is designed or approved to establish primary immunity against chickenpox
What You Should Do
Complete the two-dose varicella vaccine series according to these schedules 1, 7:
- If you're under 13 years: Get the second varicella vaccine dose at least 3 months after the first (ideally at age 4-6 years)
- If you're 13 years or older: Get the second varicella vaccine dose at least 28 days after the first
Then, when age-appropriate, receive zoster vaccination 7:
- Age 50+ years: Two-dose series of Shingrix (RZV) 2-6 months apart
- This should be done regardless of previous varicella vaccination history
Common Pitfalls to Avoid
Don't assume zoster vaccine provides chickenpox immunity: The vaccines target different aspects of VZV immunity—varicella vaccine establishes primary immunity, while zoster vaccines boost existing immunity to prevent reactivation
Don't skip the second varicella dose: Even if you've received a zoster vaccine, you still need that second varicella vaccine dose if you only had one. The guideline explicitly states "for people who previously received only 1 dose of varicella vaccine, a second dose is necessary to provide evidence of immunity" 1
Timing matters: If you've already received a zoster vaccine but only had one varicella dose, you should still get the second varicella vaccine dose to complete the series—there's no contraindication to this sequence
The Bottom Line
With only one varicella vaccine dose, you have approximately 80-85% protection against chickenpox—leaving you with a 15-20% risk of breakthrough infection 1. Adding a zoster vaccine does not close this gap because zoster vaccines are mechanistically different and not designed for primary varicella prevention. Complete your two-dose varicella vaccine series to achieve the 98% protection rate and near-complete protection against severe disease 1, 2.