Shingles and chickenpox are caused by the same virus: varicella-zoster virus (VZV).
Chickenpox is the initial infection; shingles is a reactivation of the dormant virus decades later.
So the two vaccines target the same pathogen but serve different purposes.
An adult who had chickenpox as a child does not need the chickenpox vaccine already being immune.
Getting the shingles vaccine (Shingrix) is recommended around age 50+ to prevent reactivation.
If you’re a child or young adult who never had chickenpox one should get the chickenpox vaccine (Varivax) first.
This protects against the initial infection.
Then, decades later, the shingles vaccine becomes relevant.
These vaccines are not Interchangeable.
The chickenpox vaccine (Varivax) uses a live attenuated virus and prevents the primary infection.
The shingles vaccine (Shingrix) is a recombinant subunit vaccine that is much more powerful, designed to boost immunity in people who already carry the dormant virus.
Getting Shingrix does not substitute for the chickenpox vaccine in someone who has never been exposed, because it’s not designed to prevent an initial VZV infection.
The chickenpox (varicella) vaccine and shingles (zoster) vaccine prevent different manifestations of the same virus (varicella-zoster virus), target different age groups, and differ significantly in composition and dosing.
The chickenpox vaccine prevents primary varicella infection in children and susceptible adults, while the shingles vaccine prevents reactivation of latent virus in older adults who have already had chickenpox or been vaccinated against it.
The chickenpox vaccine (Varivax) is a live attenuated varicella-zoster virus vaccine containing 1,000-17,000 plaque-forming units (PFU) per dose.
The currently available shingles vaccine (Shingrix, recombinant zoster vaccine or RZV) is a non-live, recombinant subunit vaccine containing VZV glycoprotein E with an adjuvant.
Notably, the older live attenuated zoster vaccine (Zostavax) contained the same virus as the chickenpox vaccine but at a much higher concentration—over 14-fold more PFU per dose—but is no longer available in the United States as of 2020. The chickenpox vaccine is indicated for active immunization starting at 12 months of age to prevent primary varicella infection.
The shingles vaccine (RZV) is recommended for adults aged 50 years and older to prevent herpes zoster and its complications, particularly postherpetic neuralgia.
RZV is also recommended for immunocompromised adults aged 19 years and older.
Dosing Schedule
Chickenpox vaccine requires two doses: for children 12 months to 12 years, the first dose is given at 12-15 months and the second at 4-6 years (minimum 3 months apart); for adolescents and adults, two doses are given at least 4 weeks apart.
The shingles vaccine (RZV) is administered as two doses given 2-6 months apart (minimum 4 weeks), regardless of previous herpes zoster history or prior receipt of the old live zoster vaccine.
Efficacy
The chickenpox vaccine demonstrates 94-98% efficacy against varicella, with two doses providing superior protection (98% efficacy) compared to one dose (94% efficacy) over 10 years.
The shingles vaccine (RZV) shows >90% efficacy in preventing herpes zoster across all age groups, including 97.2% efficacy in adults aged 50 years and older and 91.3% efficacy in those aged 70 years and older.
Safety Profile
The chickenpox vaccine commonly causes injection-site reactions (19%), fever ≥102°F (15%), and mild varicella-like rashes (3-4% at injection site, 4-6% generalized).
The shingles vaccine (RZV) has significant reactogenicity: injection-site pain occurs in 78% of recipients, with Grade 3 injection-site reactions in 8.5-9.5% and Grade 3 systemic reactions (myalgia, fatigue) in 6-11%.
These reactions are typically short-lived (1-3 days) and less common in those aged 80 years and older.
Contraindications
The chickenpox vaccine is contraindicated in immunosuppressed individuals, pregnant women, and those with severe allergic reactions to vaccine components.
Because RZV is a non-live vaccine, it can be safely administered to immunocompromised patients, making it suitable for a broader population including those on immunosuppressive therapy.