A live attenuated vaccine against yellow fever was developed in 1936.
Vaccine efficacy — Protective immunity occurs in 90 percent of individuals within 10 days after
receiving the 0.5 mL subcutaneous dose, and in nearly 100 percent of individuals within 3 to 4 weeks after
vaccination. Immunity after a single dose is long-lasting. The international certificate of immunization is valid
for 10 years; a booster 0.5 mL dose is required every 10 years for the certificate to be reissued.
Adverse effects — More than 550 million doses of vaccines have been administered since the 17D
vaccine strain was developed. Serious adverse reactions to the 17D vaccine include two syndromes, known as yellow
fever vaccine-associated neurotropic disease (YEL-AND) and yellow fever vaccine-associated viscerotropic disease
(YEL-AVD), the risk is higher in elderly individuals.
Mild fever, headache, myalgia and malaise, and soreness at the site of inoculation can occur in the absence of
liver function abnormalities. The vaccine is contraindicated for persons with known egg allergy. The yellow fever
vaccine virus may be transmitted by transfusion of blood products. Vaccine recipients should defer blood product
donation for two weeks.
YEL-AND — YEL-AND refers to yellow fever vaccine-associated neurotropic disease, an
encephalitis caused by infection of the central nervous system with 17D virus. Onset occurs 2 to 8 days after
vaccination; the event is nearly always self-limited. A few cases of Guillain-Barré and acute disseminated
encephalomyelitis have also been described.
This complication has been observed in infants and adults. Cases in infants have diminished since restriction of
vaccine administration to children older than nine months of age.
YEL-AVD — YEL-AVD refers to yellow fever vaccine-associated viscerotropic disease, a syndrome
resembling wild-type yellow fever infection that occurs in the setting of yellow fever 17D vaccination. Onset of
illness occurs 3 to 5 days after vaccination with fever, malaise, jaundice, oliguria, cardiovascular instability
This emphasizes the importance of careful assessment for vaccination need based on full understanding of disease
epidemiology and travel itinerary, to avoid unnecessary risk of vaccine adverse effects but to ensure that patients
with risk for exposure are protected.
Two acquired host factors appear to increase the risk of developing YEL-AVD after vaccination: advanced age and
Whom to vaccinate — In accordance with the Centers for Disease Control and Prevention (CDC),
the United States Advisory Committee on Immunization Practices (ACIP), and the World Health Organization (WHO), we
recommend vaccination for travelers to yellow fever endemic areas of Africa and
South America, and for residents of those areas as adverse events (particularly in persons >60 years of
age), the benefit of immunization should be established based on careful review of the traveler's itinerary with
respect to potential for exposure to yellow fever virus. Individuals traveling in rural areas of countries within
yellow fever endemic zones should be immunized even in the absence of official yellow fever reports, since active
transmission may be under recognized.
Vaccination against yellow fever in endemic areas is performed as part of the Expanded Program of Immunization
at nine months of age. In some African countries catch-up mass vaccination campaigns are undertaken based on
assessments of geographic risk, as part of an initiative spear headed by the World health organization to increase
vaccine coverage. Mass campaigns are also conducted in response to outbreaks in Africa and South America.
Certificates — In the United States the vaccine is distributed only through approved
Some countries in yellow fever endemic zones require an International Certificate of Vaccination as evidence of
yellow fever immunization prior to entry; in addition, some countries outside of yellow fever
zones also require evidence of immunizations prior to entry for individuals with recent travel in endemic
countries. The international certificate of immunization is valid for 10 years; a booster 0.5 mL dose is required
every 10 years for the certificate to be reissued.
Individuals with allergy to egg proteins may receive a waiver letter from a physician for travel to areas where
the risk of disease is low but vaccination is an international travel requirement.
Pregnancy and breast feeding — Yellow fever 17D vaccine is contraindicated for use in pregnant
women. Administration of yellow fever vaccine to breast-feeding women should be avoided except in situations where
exposure to yellow fever viruses cannot be avoided or postponed. Yellow fever vaccine virus can be transmitted via
Immunocompromised individuals — Yellow fever 17D vaccine should not be administered to
immunocompromised individuals because of theoretical concerns about live attenuated virus vaccines.
Contraindications include inherited immune deficiency, lymphoma, leukemia, HIV/AIDS with low CD4 counts,
immunosuppressive chemotherapy or radiotherapy, thymus disorders, DiGeorge's syndrome, and a history of thymectomy.
Travelers with asymptomatic HIV infection may be immunized if potential exposure warrants; such patients should be
advised of the possible risks of vaccination. Waiver letters can also be obtained for these patients.
Immune globulin — There is no specific yellow fever immune globulin product available. Immune
globulin produced in the United States (where many military personnel have been vaccinated) frequently contains
adequate titers of yellow fever neutralizing antibodies (typically 1:320). Passive immunization has been used off
label to protect persons traveling to high-risk areas who have contraindications to vaccination.
TripsEtc Travel & Vaccines Clinic is a full service Vaccination and Immunization Center
providing Yellow Fever Vaccine and all vaccines required for travel for residents located in Maryland and
Washington, DC. Our service area includes: Prince George's (PG) County, Maryland, Washington, DC, Baltimore
Bethesda, Bowie, Capitol Heights, Cheverly, Clinton, College Park, Columbia, Greenbelt, Hyattsville, Lanham,
Largo, Laurel, New Carrollton, Riverdale, Rockville, and Silver Spring, MD. Zip Codes: 20742, 20717, 20718,
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