Can 4-year-old and 5-year-old boys who are close contacts of a family member with chickenpox (varicella) receive the varicella vaccine after exposure?

Post-Exposure Varicella Vaccination for Household Contacts

Yes, both the 4-year-old and 5-year-old boys should receive varicella vaccine immediately, ideally within 3 days of exposure to their mother's chickenpox, as this provides >90% protection against disease and is the recommended post-exposure prophylaxis for healthy children without evidence of immunity. 1

Timing and Effectiveness

The vaccine should be administered as soon as possible, with optimal timing being within 3 days of exposure:

• Vaccination within 3 days of exposure is >90% effective in preventing varicella disease 1
• Vaccination within 5 days is 70% effective in preventing disease and 100% effective in modifying severe disease 1
• The household setting represents the highest-risk exposure, with approximately 85% (range: 65%-100%) of susceptible household contacts developing varicella after exposure 2

Rationale for Immediate Vaccination

Household exposure constitutes the most significant risk for varicella transmission:

• Persons with continuous exposure to household members with varicella are at greatest risk for infection 2
• The attack rate in household settings is substantially higher than other exposure types (approximately 5 times higher than school or hospital exposure) 2
• Direct, face-to-face contact with an infectious household member while indoors qualifies as substantial exposure 2

Safety Considerations

Post-exposure vaccination is safe for healthy children and does not require special precautions:

• The varicella vaccine is licensed for healthy persons aged >12 months 2
• Both children (ages 4 and 5) fall within the recommended age range for routine varicella vaccination 2
• No contraindications exist for vaccinating healthy children after household exposure 2

Dosing Schedule

If these children have not previously received varicella vaccine, they should receive their first dose immediately:

• Children 12 months through 12 years should receive two 0.5-mL doses of varicella vaccine administered subcutaneously, separated by at least 3 months 2
• The first dose should be given immediately for post-exposure prophylaxis 1
• The second dose should be scheduled according to the routine 2-dose recommendation 2

Important Caveats

VariZIG (varicella-zoster immune globulin) is NOT indicated for these healthy children:

• VZIG is reserved for immunocompromised patients, neonates with specific maternal exposure timing, and premature infants—not healthy children 2
• Healthy children should receive vaccine, not passive immunization 1

Monitor for breakthrough disease despite vaccination:

• Even with post-exposure vaccination, some children may develop mild breakthrough varicella 2
• Breakthrough cases typically present with <50 lesions, shorter duration, and lower fever than unvaccinated cases 2