REQUIRED IMMUNIZATIONS: YELLOW FEVER

Immunization against yellow fever is required by certain countries for entry, according to WHO regulations. Yellow fever is a rare but potentially fatal viral infection that is endemic in equatorial Africa and South America, where the virus is transmitted by day-biting mosquito vectors. The clinical presentation of the disease ranges from a mild febrile illness to a life-threatening disease characterized by hepatitis, renal failure, hemorrhagic fever, and shock. Case-fatality rates range from 23% (sub-Saharan Africa) to 65% (South America). The CDC and WHO regularly publish listings of areas with current yellow fever activity.
Yellow fever vaccination is required for entry by many countries within the areas of endemicity. Other countries may require proof of vaccination if one is traveling from an endemic area to prevent introduction of the disease. It is important to note that several countries within the yellow fever endemic zones do not require the immunization. Thus, immunization should be based on risk of exposure and not requirements. Practitioners can obtain country-specific requirements for yellow fever vaccination from the CDC’s Health Information for International Travel. Yellow fever vaccine is recommended for persons older than 9 months of age who plan to live in or travel to areas where yellow fever is reported. Vaccination is also recommended for travel in rural areas of countries that do not officially report yellow fever but that lie within the endemic zone. For purposes of international travel, the vaccine must be administered at an approved yellow fever vaccination center. A list of these centers can be obtained from local or state departments of health. The vaccine is valid for 10 years and should be documented on the Official International Certificate of Vaccination Against Yellow Fever. The yellow fever vaccine (YF-VAX, Aventis Pasteur) is a live-attenuated virus preparation made from the 17D yellow fever strain grown in chick embryo cultures. It is delivered as a single subcutaneous inoculation of 0.5 mL and induces neutralizing antibodies in 99% of recipients within 30 days of receipt. Immunity is likely lifelong, but, as mentioned, revaccination is required at 10-year intervals.
Reactions to the yellow fever vaccine are generally mild and include headaches, myalgias, and low-grade fevers. However, an analysis of yellow fever vaccine recipients in the United States from 1990 to 1998 found that persons 65 years of age or older were at an increased risk for neurologic or systemic reactions. Thus, the vaccine’s use should be considered carefully in this population and given only to those traveling to areas that report yellow fever. Yellow fever vaccination is not recommended in immunocompromised persons or in those with egg allergies. Vaccination should also be avoided in pregnancy, and non-immune women should postpone travel to high-transmission areas until after delivery. If the travel itinerary of a pregnant woman does not present a substantial risk, and immunization is required only for entry, the pregnant traveler should be given a waiver letter from her physician. Pregnant women who must travel to areas with active ongoing transmission should be vaccinated, since it is believed that the small risk to the mother and fetus from the vaccine is outweighed by the risk of yellow fever. Serologic response to yellow fever vaccine is not inhibited by administration of other vaccines, although if live virus vaccines (varicella, MMR) are not given concurrently, their administration should be separated by 1 month.
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REQUIRED IMMUNIZATIONS: YELLOW FEVERImmunization against yellow fever is required by certain countries for entry, according to WHO regulations. Yellow fever is a rare but potentially fatal viral infection that is endemic in equatorial Africa and South America, where the virus is transmitted by day-biting mosquito vectors. The clinical presentation of the disease ranges from a mild febrile illness to a life-threatening disease characterized by hepatitis, renal failure, hemorrhagic fever, and shock. Case-fatality rates range from 23% (sub-Saharan Africa) to 65% (South America). The CDC and WHO regularly publish listings of areas with current yellow fever activity.Yellow fever vaccination is required for entry by many countries within the areas of endemicity. Other countries may require proof of vaccination if one is traveling from an endemic area to prevent introduction of the disease. It is important to note that several countries within the yellow fever endemic zones do not require the immunization. Thus, immunization should be based on risk of exposure and not requirements. Practitioners can obtain country-specific requirements for yellow fever vaccination from the CDC’s Health Information for International Travel. Yellow fever vaccine is recommended for persons older than 9 months of age who plan to live in or travel to areas where yellow fever is reported. Vaccination is also recommended for travel in rural areas of countries that do not officially report yellow fever but that lie within the endemic zone. For purposes of international travel, the vaccine must be administered at an approved yellow fever vaccination center. A list of these centers can be obtained from local or state departments of health. The vaccine is valid for 10 years and should be documented on the Official International Certificate of Vaccination Against Yellow Fever. The yellow fever vaccine (YF-VAX, Aventis Pasteur) is a live-attenuated virus preparation made from the 17D yellow fever strain grown in chick embryo cultures. It is delivered as a single subcutaneous inoculation of 0.5 mL and induces neutralizing antibodies in 99% of recipients within 30 days of receipt. Immunity is likely lifelong, but, as mentioned, revaccination is required at 10-year intervals.Reactions to the yellow fever vaccine are generally mild and include headaches, myalgias, and low-grade fevers. However, an analysis of yellow fever vaccine recipients in the United States from 1990 to 1998 found that persons 65 years of age or older were at an increased risk for neurologic or systemic reactions. Thus, the vaccine’s use should be considered carefully in this population and given only to those traveling to areas that report yellow fever. Yellow fever vaccination is not recommended in immunocompromised persons or in those with egg allergies. Vaccination should also be avoided in pregnancy, and non-immune women should postpone travel to high-transmission areas until after delivery. If the travel itinerary of a pregnant woman does not present a substantial risk, and immunization is required only for entry, the pregnant traveler should be given a waiver letter from her physician. Pregnant women who must travel to areas with active ongoing transmission should be vaccinated, since it is believed that the small risk to the mother and fetus from the vaccine is outweighed by the risk of yellow fever. Serologic response to yellow fever vaccine is not inhibited by administration of other vaccines, although if live virus vaccines (varicella, MMR) are not given concurrently, their administration should be separated by 1 month.*182/348/5*

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