Vaccine‑Preventable Disease Guide: Varicella (Chickenpox)
Overview
Varicella, commonly known as chickenpox, is an acute, highly contagious viral infection caused by the varicella‑zoster virus (VZV). Before the introduction of the varicella vaccine in the mid‑1990s, the disease affected nearly 4 million people in the United States each year, leading to an average of 10,600 hospitalizations and 100–150 deaths annually [1]. Worldwide, the World Health Organization estimates that >90 % of children become infected before age 15 in regions without universal vaccination.
While anyone can contract varicella, it is most common in children ages 5–9. Adults who have never been infected or vaccinated are at higher risk for severe disease. Immunocompromised individuals (e.g., those receiving chemotherapy, organ‑transplant recipients, or people living with HIV) and pregnant women are especially vulnerable.
Symptoms
The incubation period ranges from 10‑21 days after exposure. Symptoms usually appear in three stages and may overlap.
- Prodromal stage (1‑2 days): low‑grade fever, malaise, loss of appetite, and mild headache.
- Rash stage (3‑7 days):
- Red “macules” (flat spots) that quickly become fluid‑filled vesicles.
- Vesicles break open, crust over, and form “dew‑drop on a rose petal” lesions.
- Rash appears first on the face, scalp, and trunk, then spreads to the extremities.
- Resolution stage (1‑2 weeks): lesions crust and fall off without scarring in most cases.
Other possible signs include:
- Fever up to 40 °C (104 °F)
- Itching (pruritus)
- Generalized aching muscles or joints
- Headache or photophobia
- Rare neurologic symptoms: dizziness, seizures, or encephalitis
Causes and Risk Factors
Cause: The disease is caused by primary infection with VZV, a member of the herpesvirus family. The virus spreads through respiratory droplets, direct contact with lesion fluid, or contaminated objects (fomites).
Risk factors for severe disease:
- Age ≥ 12 years (adults have a 5‑10‑fold higher risk of complications)
- Pregnancy – infection during the first 20 weeks increases risk of congenital varicella syndrome
- Immunosuppression (cancer, transplant, long‑term steroids)
- Chronic lung or heart disease
- Living in crowded settings (day‑care centers, schools, prisons)
- Absence of vaccination or prior infection
Diagnosis
Diagnosis is primarily clinical, based on the characteristic rash and epidemiologic history. Laboratory confirmation is reserved for atypical presentations or high‑risk patients.
Clinical assessment
- History of exposure within the past 3 weeks
- Physical exam documenting lesion “crops” (lesions in different stages)
Laboratory tests
- Polymerase chain reaction (PCR): Detects VZV DNA from lesion swabs; gold standard for specificity.
- Direct fluorescent antibody (DFA) test: Rapid bedside test, less sensitive than PCR.
- Serology: Paired acute‑ and convalescent‑phase IgM/IgG titers; useful when rash is atypical.
- Complete blood count (CBC): May show lymphocytosis; helps assess severity.
Treatment Options
Most healthy children recover without treatment. Therapy is targeted at reducing symptom severity, preventing complications, and limiting viral spread.
Antiviral medication
- Acyclovir: Oral 800 mg five times daily for 5 days (or 20 mg/kg q8h in children). Most effective when started <24 hours after rash onset.
- Valacyclovir: 1 g orally twice daily for 5 days (adults) – offers better bioavailability.
- Intravenous acyclovir is reserved for immunocompromised patients, severe pneumonia, or encephalitis.
Evidence from the CDC and Cochrane reviews indicates that antivirals shorten fever by ~1 day and reduce the risk of new lesions by 30‑40 % when given early [2].
Symptomatic care
- Antipyretics (acetaminophen or ibuprofen) for fever and discomfort – avoid aspirin in children due to Reye’s syndrome risk.
- Topical calamine lotion or oatmeal baths to relieve itching.
- Oral antihistamines (diphenhydramine) if pruritus interferes with sleep.
- Hydration and rest.
Isolation & infection control
- Stay home from school, work, or daycare until all lesions have crusted (usually 5‑7 days after rash onset).
- Practice regular hand‑washing, use disposable tissues, and avoid sharing personal items.
Living with Vaccine‑Preventable Disease (Varicella)
Even after the acute phase, patients may need guidance on recovery and preventing secondary spread.
- Skin care: Keep lesions clean; apply gentle soap and pat dry. Avoid scratching to prevent bacterial superinfection.
- Nutrition: A balanced diet rich in vitamins A, C, and zinc supports immune healing.
- Activity: Light activity is fine once fever resolves; avoid intense exercise if lesions are extensive.
- Psychosocial: Children may feel embarrassed; reassure them that the rash is temporary and non‑contagious once crusted.
- Vaccination reminder: If you recovered from natural infection, you are considered immune. However, the two‑dose varicella vaccine is preferred for lifelong protection and is safe even after disease.
Prevention
Vaccination is the cornerstone of varicella prevention.
Vaccination schedule
- First dose: At 12‑15 months of age.
- Second dose: At 4‑6 years of age (or ≥3 months after the first dose if given later).
- Adults without evidence of immunity should receive two doses, 4–8 weeks apart.
The CDC reports that the two‑dose regimen is >98 % effective at preventing any disease and >99 % effective at preventing severe disease [3].
Other preventive measures
- Isolation of infected individuals until lesions crust.
- Hand hygiene and surface disinfection in homes and schools.
- Avoiding exposure for pregnant women, newborns, and immunocompromised persons.
- Post‑exposure prophylaxis:
- VZV‑immune globulin (VZIG) within 96 hours for high‑risk contacts.
- One‑dose varicella vaccine within 3‑5 days of exposure for otherwise healthy, non‑immune individuals.
Complications
Most cases resolve without sequelae, but complications can be serious, especially in high‑risk groups.
- Bacterial superinfection: Staphylococcus aureus or Streptococcus pyogenes can infect lesions, leading to cellulitis or abscess.
- Pneumonia: More common in adults and immunocompromised patients; can require hospitalization.
- Encephalitis: Occurs in ~1 per 10,000 cases; presents with confusion, seizures, or focal neurologic deficits.
- Hepatitis: Transient elevation of liver enzymes; rarely progresses to fulminant hepatitis.
- Reye’s syndrome: Historically linked to aspirin use in children with viral illness; avoid aspirin.
- Congenital varicella syndrome: If maternal infection occurs in the first 20 weeks, the fetus may develop limb hypoplasia, eye defects, or neurologic abnormalities.
- Reactivation (shingles): VZV can lie dormant and reactivate later as herpes zoster, particularly in older adults.
When to Seek Emergency Care
- Difficulty breathing, wheezing, or rapid breathing
- High fever (> 40 °C or 104 °F) that does not respond to medication
- Severe headache, stiff neck, or changes in mental status (confusion, lethargy, seizures)
- Persistent vomiting or inability to keep fluids down
- Rapidly spreading rash with signs of bacterial infection (significant redness, swelling, pus, or pain)
- Sudden onset of severe abdominal pain
- Bleeding from the eyes, nose, or gums
- Pregnant woman with a fever or rash – risk to the fetus
Early intervention can prevent life‑threatening complications such as pneumonia, encephalitis, or disseminated infection.
References
- Mayo Clinic. “Chickenpox (varicella).” Updated 2023. https://www.mayoclinic.org
- CDC. “Varicella (Chickenpox) – Antiviral Treatment.” 2022. https://www.cdc.gov
- World Health Organization. “Varicella vaccine: WHO position paper, March 2022.” https://www.who.int
- Cochrane Review. “Antiviral agents for chickenpox.” 2021. https://www.cochranelibrary.com
- National Institutes of Health. “Varicella: Clinical Presentation and Management.” 2024. https://www.ncbi.nlm.nih.gov