Varicella vaccine !
Live attenuated varicella-zoster virus (Oka strain). It prevents chickenpox and is also used soon after exposure.
Updated 2026-11-01
Also called: Chickenpox vaccine, VAR, MMRV (with measles, mumps, rubella)
The figure shows the gE domain of varicella-zoster virus bound to a human antibody fragment; the live vaccine induces antibodies against gE and other viral glycoproteins.
Mechanism of action
The attenuated virus replicates weakly and induces antibodies and cellular immunity against the viral glycoproteins, preventing chickenpox or making it milder. Vaccine virus spreads to others only rarely, mainly from a person who develops a vaccine rash.
- Attenuated Oka virus is injected and replicates weakly
- Antibodies and T cells form against viral glycoproteins
- Immunity prevents chickenpox or makes it milder
- Given soon after exposure, it can prevent or soften disease
Pharmacokinetics
- Onset and duration
- After exposure it is given within three to five days to prevent or soften disease
Indications
- Routine prevention of chickenpox in children and in susceptible adolescents and adults
- Post-exposure prophylaxis in susceptible people aged 12 months or older
Adverse effects
Common
- Pain and redness at the injection site
- Mild varicella-like rash
- Fever
Contraindications
- Pregnancy
- Immunosuppression (low-dose or topical steroids are exceptions)
- Severe allergic reaction to a previous dose or a component (gelatin, neomycin)
Key interactions
- Aciclovir, valaciclovir, famciclovir
- They can block replication of the vaccine virus: avoided in the day before vaccination
- Acetylsalicylic acid and other salicylates
- Avoided for six weeks after vaccination because of Reye syndrome
- Antibody-containing blood products
- They neutralise the vaccine virus: vaccination is delayed for months
What is monitored
- Rash after vaccination; keep lesions covered and avoid contact with immunosuppressed people
- Two documented doses
Administration and safety
- Reconstitute with the supplied diluent only
- Subcutaneous route
- Do not confuse varicella vaccine with zoster vaccine: different products and indications
- Record the batch and product
Nursing care
- Ask about pregnancy, immunosuppression and recent blood products
- Ask about antiherpetic drugs before vaccination
- Teach families to avoid acetylsalicylic acid for six weeks
- If a rash appears, cover the lesions and avoid immunosuppressed contacts
Pregnancy and breastfeeding
Contraindicated in pregnancy, and pregnancy is avoided for one month after each dose; maternal chickenpox early in pregnancy can cause congenital varicella syndrome.
Test yourself
Think of the answer, then tap the question to see it.
Why are salicylates avoided after varicella vaccine?
Varicella (wild or vaccine virus) with salicylates is associated with Reye syndrome.
Why are antiherpetic drugs avoided just before varicella vaccine?
Aciclovir and related drugs inhibit replication of the live vaccine virus and can weaken the response.
What is used for post-exposure protection in a susceptible person who cannot receive the live vaccine?
Varicella-zoster immunoglobulin (for example in immunosuppression, pregnancy without immunity or some newborns).
Related drugs
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Chapter 22: Varicella | Pink Book | CDC (Centers for Disease Control and Prevention, 2021); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.