Yellow Fever
Disease and Vaccine Information

Yellow fever occurs only in Africa and South America. In South America sporadic infections occur almost exclusively in forestry and agricultural workers who are exposed occupationally in or near forests. In Africa the virus is transmitted in three geographic regions:

  • principally and foremost, in the moist savanna zones of West and Central Africa during the rainy season,
  • secondly, outbreaks occur occasionally in urban locations and villages in Africa,
  • and finally, to a lesser extent, in jungle regions.
Yellow fever is a viral disease transmitted between humans by a mosquito. Yellow fever is a very rare cause of illness in travelers, but most countries have regulations and requirements for yellow fever vaccination that must be met prior to entering the country.

General precautions to avoid mosquito bites should be followed. These include the use of insect repellent, protective clothing, and mosquito netting.

Yellow fever vaccine is a live virus vaccine. A single dose confers long-lived immunity lasting 10 years or more. Administration of immune globulin does not interfere with the antibody response to yellow fever vaccine. This vaccine has been used for several decades and has a very low rate of adverse reactions associated with it.

One dose of yellow fever vaccine may be administered to adults and children over 9 months of age. This vaccine is only administered at designated yellow fever centers, usually your local health department. Consult your local health department for yellow fever vaccination sites near you. The CDC does not keep a list of registered yellow fever vaccination sites. If at continued risk of yellow fever infection, a booster dose is needed every 10 years.

WHO SHOULD NOT RECEIVE THE YELLOW FEVER VACCINE
The vaccine generally is associated with few side effects; fewer than 5% of vaccinees develop mild headache, muscle pain, or other minor symptoms 5 to 10 days after vaccination.

Under almost all circumstances, there are four groups of people who should not receive the vaccine unless the risk of yellow fever disease exceeds the small risk associated with the vaccine. In most cases, these people should obtain either a waiver letter prior to travel or their travel to an area with active yellow fever transmission should be delayed:

  1. Yellow fever vaccine should never be given to infants under 6 months of age due to a risk of developing viral encephalitis. In most cases, vaccination should be deferred until 9 to 12 months of age, unless the risk of yellow fever infection outweighs the risk of vaccine side effects in very young infants.
  2. Pregnant women should not be vaccinated because of a theoretical risk that the developing fetus may become infected from the vaccine unless the risk of yellow fever infection outweighs the risk of live virus vaccine side effects to pregnant women.
  3. Persons hypersensitive to eggs should not receive the vaccine because it is prepared in embryonated eggs. If vaccination of a traveler with a questionable history of egg hypersensitivity is considered essential, an intradermal test dose may be administered under close medical supervision. [Notify your doctor prior to vaccination if you think that you may be allergic to the vaccine or to egg products.]
  4. Persons with an immunosuppressed condition associated with AIDS or HIV infection, or those with their immune system altered by either diseases such as leukemia and lymphoma or through drugs and radiation should not receive the vaccine. People with asymptomatic HIV infection may be vaccinated if exposure to yellow fever cannot be avoided.
If you have one of these conditions, your doctor will be able to help you decide whether you should be vaccinated, should delay your travel, or should obtain a waiver.

In all cases the decision to immunize an infant between 6 and 9 months of age, a pregnant woman, or an immunocompromised patient should be made on an individual basis. The physician should weigh the risks of exposure and contracting the disease, against the risks of immunization, and possibly consider alternative means of protection.

Medical Waivers
Most countries will accept a medical waiver for persons with a medical reason for not receiving the vaccination. CDC recommends obtaining written waivers from consular or embassy officials before departure. Travelers should contact the embassy or consulate for specific advice. Typically, a physician's letter stating the reason for withholding the vaccination and written on letterhead stationery is required by the embassy or consulate. The letter should bear the stamp used by a health department or official immunization center to validate the International Certificate of Vaccination.

Yellow Fever Vaccination requirements and recommendations are given in CDC's regional travel documents, such as "Tropical South America," "West Africa," etc. A country-by-country listing of Yellow Fever Vaccination Requirements is provided in the document "Comprehensive Yellow Fever Vaccination Requirements."

Yellow Fever Certificate
After immunization an International Certificate of Vaccination is issued and is valid 10 days after vaccination to meet entry and exit requirements for all countries. The Certificate is good for 10 years. You must take the Certificate with you. Travelers who have a medical reason not to receive the yellow fever vaccine should obtain a medical waiver. Most countries will accept a medical waiver for persons with a medical reason not to receive the vaccine. When required, CDC recommends obtaining written waivers from consular or embassy officials before departure. A physician's letter clearly stating the medical reason not to receive the vaccine, might be acceptable to some governments. It should be written on letterhead stationery and bear the stamp used by a health department or official immunization center to validate the International Certificate of Vaccination. Check embassies or consulates for specific waiver requirements.