What is the management plan for a vaccinated individual exposed to varicella (chickenpox)?

Management of Vaccinated Individuals Exposed to Chickenpox

Vaccinated individuals exposed to varicella should receive a second dose of vaccine within 3-5 days of exposure if they have only received one dose (provided ≥4 weeks have elapsed since the first dose), while those who have received two doses require monitoring only—no additional intervention is needed. 1

Risk Stratification Based on Vaccination Status

Two-Dose Vaccine Recipients (Fully Vaccinated)

• No postexposure prophylaxis is required for individuals who have received 2 doses of varicella vaccine 1
• Monitor daily during days 8-21 (or days 10-21) after exposure for fever, skin lesions, and systemic symptoms suggestive of varicella 1, 2
• Monitoring can be performed directly by occupational health programs or through self-reporting of fever, headache, constitutional symptoms, or atypical skin lesions 1
• Exclude from work/school immediately if any symptoms develop 1
• No work restrictions are needed if exposure was to localized herpes zoster with covered lesions 1

One-Dose Vaccine Recipients (Partially Vaccinated)

• Administer the second dose within 3-5 days after exposure to rash, provided at least 4 weeks have elapsed since the first dose 1
• This second dose may modify disease if infection has not yet occurred and is >90% effective at preventing disease 3, 2
• After receiving the second dose, manage identically to two-dose recipients with daily monitoring during days 8-21 1
• If the second dose is not given or is given >5 days after exposure, exclude from work/school for days 8-21 after exposure 1

Unvaccinated Individuals Without Evidence of Immunity

• Administer varicella vaccine as soon as possible, ideally within 3-5 days of exposure 1, 3, 4
• Vaccination within this window is >90% effective at preventing disease 4, 2
• Vaccination >5 days postexposure is still indicated as it provides protection against subsequent exposures (if current exposure did not cause infection) 1
• Exclude from work/school during days 8-21 after exposure as they are potentially infective during this period 1

Special Populations Requiring Alternative Prophylaxis

High-Risk Individuals Who Cannot Receive Vaccine

For pregnant women, immunocompromised patients, and premature infants (<28 weeks gestation or <1,000g) who are exposed:

• Administer Varicella-Zoster Immune Globulin (VZIG) within 96 hours of exposure (can be extended to 10 days per CDC guidelines) 3, 4
• VZIG is strongly preferred over vaccination for pregnant women exposed to varicella 3
• Dosing: 125 IU/10 kg body weight intramuscularly, maximum 625 IU (five vials); minimum dose 62.5 IU for infants ≤2.0 kg 4
• VZIG may prolong the incubation period by one week, extending the monitoring/exclusion period from 21 to 28 days 1
• If varicella develops despite VZIG, initiate antiviral therapy immediately 4

Alternative Prophylaxis When VZIG is Unavailable

• If VZIG is unavailable or >96 hours post-exposure, consider acyclovir 20 mg/kg (maximum 800 mg) four times daily for 5-7 days, initiated 7-10 days after exposure 3, 4

Critical Pitfalls to Avoid

• Do not confuse the timing windows: Varicella vaccine is effective within 3-5 days of exposure, while treatment with acyclovir for active disease must be initiated within 24 hours of rash onset 3, 4
• Birth before 1980 is NOT considered evidence of immunity for healthcare personnel due to the risk of nosocomial transmission to high-risk patients 1
• Do not use acyclovir prophylactically in otherwise healthy vaccinated individuals—vaccination is the method of choice for postexposure prophylaxis 4
• Recognize that vaccinated individuals who develop breakthrough varicella are contagious and can sustain transmission, despite having milder disease 5, 6
• Routine serologic testing after 2 doses of vaccine is not recommended for management of vaccinated individuals, as available commercial assays are not sensitive enough to detect antibody after vaccination in all instances 1

Healthcare Setting Considerations

• Healthcare institutions should ensure all personnel have evidence of immunity to varicella through documentation of 2 doses of vaccine 1
• Serologic screening before vaccination of personnel with negative or uncertain history is likely cost-effective 1
• Airborne and contact precautions are required for all hospitalized patients with varicella until all lesions are dry and crusted 3
• Patients are infectious up to 2 days before rash onset through lesion crusting, typically 5-7 days after rash onset 3, 2