Yellow Fever Vaccine Recommendations
Yellow fever vaccine is recommended for persons aged ≥9 months who are traveling to or living in areas at risk for yellow fever virus transmission in South America and Africa. 1
Target Populations
The primary target populations for yellow fever vaccination include:
- Travelers to endemic areas in sub-Saharan Africa and tropical South America
- Laboratory personnel who might be exposed to yellow fever virus
- Individuals living in areas with risk of yellow fever virus transmission 1
Yellow fever is endemic to tropical regions of Africa and South America, with an estimated 200,000 cases and 30,000 deaths annually, with nearly 90% of cases occurring in Africa 2.
Dosage and Administration
- Single subcutaneous injection of 0.5 mL of reconstituted vaccine
- Must be administered at an approved yellow fever vaccination center
- International Certificate of Vaccination must be completed, signed, and validated with the center's stamp 1
- Vaccine should be stored at temperatures of 2ºC–8ºC (35ºF–46ºF) until reconstitution
- Unused reconstituted vaccine should be discarded within 1 hour 3
Duration of Protection
Historically, booster doses were required every 10 years according to International Health Regulations. However, recent evidence suggests immunity likely persists for 30-35 years or possibly for life 1. A 2024 systematic review and meta-analysis found that a single dose of yellow fever vaccination provides lifelong protection in most travelers, with pooled seroprotection rates of 94% (95% CI 86-99) among healthy adults in non-endemic settings 4.
Contraindications and Precautions
Absolute Contraindications:
- Infants younger than 6 months of age 1
- Severe hypersensitivity to vaccine components or eggs
Precautions/Relative Contraindications:
- Infants aged 6-8 months (can receive vaccination only in unavoidable high-risk situations) 1
- Adults aged ≥60 years (higher risk of serious adverse events) 1
- Pregnancy (theoretical risk to the fetus)
- Breastfeeding (theoretical risk of transmission through breast milk)
- Immunocompromised individuals
Adverse Events
Yellow fever vaccine is generally safe, but can cause:
Common mild reactions:
- Headaches, myalgia, and low-grade fevers (occur in <25% of vaccinees)
- Approximately 1% of vaccinees curtail regular activities 1
Serious adverse events (rare):
- Yellow Fever Vaccine-Associated Neurotropic Disease (YEL-AND)
- Yellow Fever Vaccine-Associated Viscerotropic Disease (YEL-AVD) - can be severe or fatal
- Immediate hypersensitivity reactions (estimated incidence of 1/130,000-250,000) 1
- Meningoencephalitis (historically considered a risk only in children <6 months, but now recognized in older children and adults, though with better prognosis) 5
Special Populations
Children:
- Not recommended for infants <9 months due to risk of encephalitis 3
- Lower long-term seroprotection rates (47%) in children vaccinated at 9-23 months of age 4
HIV-infected individuals:
- Lower long-term seroprotection rates (61%) 4
- May require booster doses
Older Adults:
- Adults ≥60 years have higher risk of serious adverse events 1
- Careful risk-benefit assessment needed
Medical Waivers
Health-care providers may issue a waiver of vaccination for travelers with contraindications to vaccination 1. A physician's letter stating the contraindication to vaccination has been acceptable to certain governments outside the United States 3. The letter should:
- Be written on letterhead stationery
- Bear the stamp used by health departments and official vaccination centers
- Travelers should obtain specific advice from the embassy or consulate of countries they plan to visit
Additional Prevention Measures
In addition to vaccination, travelers should use personal protective measures:
- Insect repellent
- Permethrin-impregnated clothing
- Staying in accommodations with screened or air-conditioned rooms 1
These measures are particularly important for individuals who cannot receive the vaccine due to contraindications.