What is the recommended dose, schedule, and contraindications for the live‑attenuated yellow‑fever vaccine (e.g., Stamaril or YF‑VAX) for travelers and residents of endemic areas?

Yellow Fever Vaccine: Dosing, Schedule, and Contraindications

Administer a single 0.5 mL subcutaneous injection of reconstituted yellow fever vaccine (17D strain) to all persons aged ≥9 months traveling to endemic areas of Africa or South America, with the vaccine providing long-lasting immunity that no longer requires routine boosters every 10 years. 1, 2, 3

Dosage and Administration

Standard Dose:

• 0.5 mL subcutaneous injection for all ages when vaccination is indicated 1, 3
• Reconstitute lyophilized vaccine with supplied sodium chloride diluent only 3
• Use within 60 minutes of reconstitution; discard unused portions after 1 hour 1, 3
• Store reconstituted vaccine at 35°F–46°F (2°C–8°C) during the 1-hour window 1

Important Administration Details:

• Must be given at an approved Yellow Fever Vaccination Center designated by state/territorial health departments 4, 3
• If inadvertently given intramuscularly (rather than subcutaneously), do not repeat the dose—immune response is not affected 1
• Observe all vaccinees for at least 15 minutes post-vaccination due to anaphylaxis risk, even in those without prior egg allergy 1

Vaccination Schedule and Timing

Primary Vaccination:

• Single dose provides long-lasting protection for most healthy individuals; routine 10-year boosters are no longer required 3, 5
• Vaccine must be administered at least 10 days before travel to ensure immunity 2, 4
• International Certificate of Vaccination or Prophylaxis (ICVP) becomes valid 10 days after vaccination and remains valid for 10 years for entry requirements 4

Booster Considerations:

• Additional doses may be considered for individuals who may not have mounted adequate initial responses: women vaccinated during pregnancy, hematopoietic stem cell transplant recipients, and HIV-infected persons 3
• Boosters may be given to laboratory personnel handling virulent virus or travelers spending prolonged periods in highly endemic areas (e.g., rural West Africa) 3
• Some countries still require proof of vaccination within 10 years for entry despite WHO guidance on single-dose immunity 3

Evidence on Duration: Research demonstrates that even older adults (≥60 years) maintain seropositivity 10 years after primary vaccination, supporting single-dose recommendations 6. However, some experts argue that a second dose may be prudent for complete protection 7.

Absolute Contraindications

Age-Related:

• Infants <6 months old: Risk of yellow fever vaccine-associated neurotropic disease (YEL-AND) is substantially elevated at 50–400 cases per 100,000 vaccinated 1, 2

Immunocompromised States:

• Primary immunodeficiencies 2, 4
• Symptomatic HIV infection 4
• Transplant recipients (solid organ or hematopoietic stem cell) 2
• Immunosuppressive therapies: High-dose corticosteroids (≥2 mg/kg or ≥20 mg/day prednisone equivalent for ≥2 weeks), alkylating drugs, antimetabolites, TNF-α inhibitors (etanercept), IL-1 blockers (anakinra), monoclonal antibodies targeting immune cells (rituximab, alemtuzumab) 1

Exception for Corticosteroids: Short-term use (<2 weeks), low-to-moderate doses (<20 mg prednisone daily), alternate-day therapy, physiologic replacement doses, or topical/inhaled/intra-articular administration are NOT contraindications 1

Precautions (Not Absolute Contraindications)

Age-Related Precautions:

• Infants 6–8 months: Two cases of YEL-AND reported; postpone travel if possible, but may vaccinate if travel unavoidable after risk-benefit assessment 1, 4
• Adults ≥60 years (especially first-time recipients): Serious adverse event rate of 8.3 per 100,000 doses vs. 4.7 per 100,000 for all ages; YEL-AND risk 1.8 per 100,000 and YEL-AVD risk 1.4 per 100,000 vs. 0.8 and 0.4 per 100,000 overall 1, 4

Pregnancy and Breastfeeding:

• Pregnancy: Vaccinate only if travel to high-risk endemic areas cannot be avoided 4
• Breastfeeding: Exercise caution; consider delaying vaccination 4

Clinical Decision-Making for Precautions: When precautions exist, weigh the risk of yellow fever disease (case-fatality 20–50% for severe disease; 10 deaths per 100,000 unvaccinated travelers to West Africa during 2-week stay) against vaccine adverse event risks 2, 4. Recent fatal cases in unvaccinated South American travelers underscore disease severity 4.

Medical Waivers and Documentation

When Vaccination is Contraindicated:

• Complete the "Medical Contraindications to Vaccination" section of the ICVP with physician signature, date, and official Yellow Fever Vaccination Center stamp 1, 4
• Critical caveat: Destination countries may refuse to accept medical waivers, potentially resulting in quarantine (up to 6 days), denied entry, or forced revaccination at the border 4
• Counsel patients on strict mosquito avoidance: EPA-registered repellents (DEET, picaridin, IR3535, oil of lemon eucalyptus), permethrin-impregnated clothing, screened/air-conditioned accommodations 2, 4

Documentation Requirements:

• ICVP must include provider signature and official yellow fever vaccination center stamp to be valid 4
• Incomplete or inaccurate certificates can cause serious travel disruptions 4
• Some countries require proof even for travelers in transit who visited endemic countries 1, 4

Common Pitfalls to Avoid

• Expired vaccine: Do not use; if inadvertently administered, repeat with valid vaccine after 28-day interval 1
• Wrong reconstitution timing: Vaccine loses potency if not used within 1 hour 1, 3
• Missing official stamp: ICVP invalid without Yellow Fever Vaccination Center validation 4
• Inadequate pre-travel timing: Vaccine given <10 days before travel may not confer immunity 2, 4
• Ignoring country-specific requirements: Entry rules vary and change frequently; verify current requirements via CDC travel website before each trip 1, 4

Adverse Events

Mild Reactions (Common):

• Headache, myalgia, low-grade fever in 2–5% of vaccinees, occurring 5–10 days post-vaccination; <0.2% curtail activities 1

Serious Adverse Events (Rare):

• YEL-AND (neurotropic disease): Encephalitis risk, especially in infants <6 months 1, 2
• YEL-AVD (viscerotropic disease): Multi-organ failure mimicking wild-type yellow fever; incidence 0.09–2.5 per 1,000 doses, potentially fatal 4
• Immediate hypersensitivity: Extremely rare; primarily in egg-allergic individuals 1

Desensitization Protocol (if vaccination imperative in egg-allergic patient): Administer successive subcutaneous doses at 15–20 minute intervals: 0.05 mL of 1:10 dilution, then 0.05 mL, 0.10 mL, 0.15 mL, and 0.20 mL of full-strength vaccine under direct physician supervision with emergency equipment available 3

Concomitant Vaccine Administration

• Administer yellow fever vaccine with other vaccines using separate syringes at separate sites; do not mix 3
• When not given concomitantly, wait at least 4 weeks between yellow fever vaccine and other live vaccines 3