Usage
Live attenuated varicella-zoster virus (VZV) vaccines are primarily used for the prevention of varicella (chickenpox) in individuals 12 months of age and older. A different formulation with a higher viral count is used for prevention of herpes zoster (shingles) in adults 50 years and older. It is classified as a viral vaccine. The vaccine works by introducing a weakened form of the varicella-zoster virus into the body, prompting an immune response without causing the full-blown illness. This immune response creates memory cells that protect against future infections with wild-type VZV.
Alternate Names
The generic name is varicella vaccine live. The brand names include Varivax, Varilrix, and Zostavax (for shingles prevention). ProQuad is a combination vaccine containing measles, mumps, rubella, and varicella components.
How It Works
Pharmacodynamics: The live attenuated VZV vaccine mimics a natural varicella infection, stimulating both humoral and cell-mediated immunity. This leads to the production of VZV-specific antibodies and the development of memory T cells that recognize and eliminate VZV-infected cells. The vaccine provides long-term protection against varicella infection, although the exact duration of immunity is unknown. Breakthrough infections can occur, but are typically mild.
Pharmacokinetics: After subcutaneous administration, the attenuated virus replicates locally at the injection site and in regional lymph nodes. The virus does not typically spread systemically. The vaccine does not integrate into the host genome. Elimination of the attenuated virus is mediated by the immune system. Specific pathways of elimination have not been characterized in detail. The vaccine does not induce CYP enzyme activity.
Dosage
Standard Dosage
Adults (13 years and older): 0.5 mL subcutaneously administered as two doses, separated by 4 to 8 weeks. Some sources recommend an interval of at least 6 weeks between doses.
Children (12 months to 12 years): 0.5 mL subcutaneously administered as two doses, separated by at least 3 months. If the second dose is given at least 28 days after the first dose, it is still considered valid.
Special Cases:
- Elderly Patients: No dose adjustment necessary. For herpes zoster prevention, a single 0.65 mL dose of Zostavax is administered subcutaneously. Zostavax is no longer available in the US.
- Patients with Renal Impairment: No specific dose adjustment is indicated.
- Patients with Hepatic Dysfunction: No specific dose adjustment is indicated.
- Patients with Comorbid Conditions: The vaccine is generally contraindicated in immunocompromised patients (e.g., those receiving immunosuppressive therapy, with primary or acquired immunodeficiency, or with active untreated tuberculosis). Individuals with asymptomatic HIV infection (CDC Class 1) with an age-specific CD4+ T-lymphocyte percentage ≥ 25% can receive two doses, separated by 12 weeks. Vaccination should be deferred for individuals with a family history of immunodeficiency until immunocompetence is confirmed.
Clinical Use Cases
The live attenuated VZV vaccine is not used in clinical situations such as intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations. Its sole purpose is for the prevention of varicella or herpes zoster.
Dosage Adjustments
No specific dose adjustments are generally recommended based on renal/hepatic dysfunction, metabolic disorders, or genetic polymorphisms. However, for immunocompromised individuals, careful consideration is required. The vaccine is contraindicated in most cases of immunocompromise.
Side Effects
Common Side Effects:
Pain, redness, and swelling at the injection site; fever; mild rash.
Rare but Serious Side Effects:
Anaphylaxis, pneumonia, encephalitis (rare).
Long-Term Effects:
Herpes zoster (shingles) can occur years after vaccination. This is due to the reactivation of the attenuated vaccine virus.
Adverse Drug Reactions (ADR):
Severe allergic reactions (anaphylaxis) require immediate medical attention.
Contraindications
- History of anaphylaxis or severe allergic reaction to any component of the vaccine (including neomycin and gelatin).
- Pregnancy. Pregnancy should be avoided for three months following vaccination.
- Immunosuppression (including active untreated tuberculosis and individuals receiving high-dose systemic corticosteroids). Individuals receiving low-dose or topical corticosteroids, as used for asthma prophylaxis, may receive the vaccine.
- Active febrile illness with fever > 38.5°C. Low-grade fever is not a contraindication.
Drug Interactions
- Immunosuppressive medications (e.g., chemotherapy, radiation therapy, high-dose corticosteroids) can reduce the efficacy of the vaccine and increase the risk of complications.
- Antiviral medications (e.g., acyclovir) can interfere with vaccine efficacy if given within 72 hours after vaccination. The recombinant zoster vaccine can be given at any time without discontinuing antiviral treatment.
- Salicylates should be avoided for 6 weeks after vaccination due to the theoretical risk of Reye’s syndrome.
- Concurrent administration with other live vaccines is generally safe, but may require separate injection sites and adherence to appropriate scheduling intervals.
Pregnancy and Breastfeeding
The varicella vaccine is contraindicated during pregnancy. Pregnancy should be avoided for three months following vaccination. The vaccine is not generally recommended for breastfeeding mothers due to the theoretical risk of transmission of the vaccine virus. However, some sources suggest it may be administered postpartum with continued breastfeeding.
Drug Profile Summary
- Mechanism of Action: Induces humoral and cell-mediated immunity against VZV.
- Side Effects: Injection site reactions, fever, mild rash (common); anaphylaxis (rare).
- Contraindications: Pregnancy, immunosuppression, severe allergic reactions to vaccine components.
- Drug Interactions: Immunosuppressants, antivirals.
- Pregnancy & Breastfeeding: Contraindicated in pregnancy; not generally recommended during breastfeeding.
- Dosage: 0.5 mL SC x 2 doses (children: 3+ months apart; adults: 4-8 weeks apart).
- Monitoring Parameters: Monitor for adverse reactions, especially allergic reactions.
Popular Combinations
The varicella vaccine is often given in combination with the MMR (measles, mumps, rubella) vaccine as MMRV.
Precautions
- Screen for contraindications before administration.
- Avoid pregnancy for three months after vaccination.
- Observe for signs of allergic reactions.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Live Attenuated Varicella-Zoster Virus?
A: Adults and adolescents (≥13 years): 0.5 mL subcutaneously x 2 doses, 4-8 weeks apart. Children (12 months–12 years): 0.5 mL subcutaneously x 2 doses, at least 3 months apart.
Q2: Can the varicella vaccine be given during pregnancy?
A: No, the varicella vaccine is contraindicated during pregnancy. Pregnancy should be avoided for three months following vaccination.
Q3: What are the most common side effects of the varicella vaccine?
A: Common side effects include soreness, redness, or swelling at the injection site; low-grade fever; or a mild rash.
Q4: Who should not receive the varicella vaccine?
A: Individuals with a history of severe allergic reaction to any vaccine component, immunocompromised individuals, pregnant women, and those with a moderate or severe acute illness should not receive the vaccine.
Q5: Can the varicella vaccine prevent shingles?
A: The varicella vaccine can reduce the risk of shingles, but a separate, higher-dose vaccine (Zostavax, now discontinued in the US, or the recombinant zoster vaccine Shingrix) is specifically indicated for shingles prevention in adults aged 50 and older.
Q6: How long does immunity last after varicella vaccination?
A: The duration of protection after varicella vaccination is not precisely known, but it is considered long-term. Breakthrough varicella infections can occur, but are typically mild.
Q7: Can the varicella vaccine be given with other vaccines?
A: Yes, the varicella vaccine can generally be administered concurrently with other vaccines, but may need to be given at a different injection site. Check recommended schedules to determine appropriate timing intervals if administering with other live vaccines.
Q8: What should I do if a patient develops a fever after receiving the varicella vaccine?
A: Low-grade fever is a common side effect and can be managed with antipyretics like acetaminophen or ibuprofen. If the fever is high or persistent, or accompanied by other symptoms, further evaluation may be needed.
Q9: Is there a risk of transmitting the vaccine virus to others?
A: Transmission of the vaccine virus is rare, but can occur. Vaccine recipients should avoid close contact with susceptible high-risk individuals (e.g., pregnant women, immunocompromised individuals).
