Last reviewed 2026-05-14 · How we verify

Merck and Company's Varivax

GlaxoSmithKline · Phase 3 active Biologic

Merck and Company's Varivax is a Live attenuated vaccine Biologic drug developed by GlaxoSmithKline. It is currently in Phase 3 development for Prevention of varicella (chickenpox) in children and adults.

Varivax is a live attenuated varicella-zoster virus vaccine that stimulates immune response to prevent chickenpox infection.

Varivax is a live attenuated varicella-zoster virus vaccine that stimulates immune response to prevent chickenpox infection. Used for Prevention of varicella (chickenpox) in children and adults.

At a glance

Generic name	Merck and Company's Varivax
Sponsor	GlaxoSmithKline
Drug class	Live attenuated vaccine
Target	Varicella-zoster virus (VZV)
Modality	Biologic
Therapeutic area	Immunology / Infectious Disease
Phase	Phase 3

Mechanism of action

The vaccine contains a weakened form of the varicella-zoster virus (Oka strain) that replicates in host cells but does not cause disease in immunocompetent individuals. This triggers both cellular and humoral immune responses, generating antibodies and T-cell memory that protect against natural varicella infection and reduce severity of breakthrough infections.

Approved indications

Prevention of varicella (chickenpox) in children and adults

Common side effects

Injection site reactions (erythema, swelling, pain)
Fever
Rash (vaccine strain varicella)
Myalgia

Key clinical trials

Immunogenicity and Safety of Kinrix + (Measles Mumps Rubella) MMR Vaccine With and Without Varicella Vaccine in Healthy Children 4-6 Years (PHASE3)

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.

Source	Used for
ClinicalTrials.gov	Trial enrolment, design, endpoints, results

Competitive intelligence

For the full competitive landscape — auto-detected comparators, recent regulatory actions across the set, upcoming PDUFA, patent timeline, sponsor landscape:

Merck and Company's Varivax CI brief — competitive landscape report
Merck and Company's Varivax updates RSS · CI watch RSS
GlaxoSmithKline portfolio CI

Frequently asked questions about Merck and Company's Varivax

What is Merck and Company's Varivax?

Merck and Company's Varivax is a Live attenuated vaccine drug developed by GlaxoSmithKline, indicated for Prevention of varicella (chickenpox) in children and adults.

How does Merck and Company's Varivax work?

Varivax is a live attenuated varicella-zoster virus vaccine that stimulates immune response to prevent chickenpox infection.

What is Merck and Company's Varivax used for?

Merck and Company's Varivax is indicated for Prevention of varicella (chickenpox) in children and adults.

Who makes Merck and Company's Varivax?

Merck and Company's Varivax is developed by GlaxoSmithKline (see full GlaxoSmithKline pipeline at /company/gsk).

What drug class is Merck and Company's Varivax in?

Merck and Company's Varivax belongs to the Live attenuated vaccine class. See all Live attenuated vaccine drugs at /class/live-attenuated-vaccine.

What development phase is Merck and Company's Varivax in?

Merck and Company's Varivax is in Phase 3.

What are the side effects of Merck and Company's Varivax?

Common side effects of Merck and Company's Varivax include Injection site reactions (erythema, swelling, pain), Fever, Rash (vaccine strain varicella), Myalgia.

What does Merck and Company's Varivax target?

Merck and Company's Varivax targets Varicella-zoster virus (VZV) and is a Live attenuated vaccine.

Drug class: All Live attenuated vaccine drugs
Target: All drugs targeting Varicella-zoster virus (VZV)
Manufacturer: GlaxoSmithKline — full pipeline
Therapeutic area: All drugs in Immunology / Infectious Disease
Indication: Drugs for Prevention of varicella (chickenpox) in children and adults
Compare: Merck and Company's Varivax vs similar drugs
Pricing: Merck and Company's Varivax cost, discount & access