Yellow fever primary prevention

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Alejandro Lemor, M.D. [2]

Overview

The two methods to prevent yellow fever are vaccination and vector control. 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. Yellow fever vaccine may be required for entry into certain countries. The best way to prevent mosquitoborne diseases, including yellow fever, is to avoid mosquito bites.

Vaccination

Yellow fever vaccine is a live-virus vaccine which has been used for several decades. A single dose protects against disease for 10 years or more. If a person is at continued risk of infection, a booster dose is recommended every 10 years.

Indication

• People aged ≥9 months who are traveling to or living in areas with risk for yellow fever virus transmission in South America and Africa.

Vaccine Administration

• For all eligible people, a single injection of reconstituted vaccine should be administered subcutaneously.
• Name: 17D yellow fever vaccine
• Trade Name: YF-Vax®
• Dose: 0.5 mL²
• Route: SC
• The International Health Regulations (IHR) published by the World Health Organization (WHO) require revaccination at 10-year intervals.
• Recommendations for storage of yellow fever vaccine include the following:

• The vaccine should be transported and stored between +2°C (35°F) and+8°C (46°F).
• Manufacturer's recommendations for vaccine storage must be observed.
• The vaccine should not be used after the expiration date printed on the vial.

• Since YF-VAX® does not contain a preservative, all reconstituted vaccine and containers must be appropriately discarded if they are not used within 1 hour. This includes the multi-dose (5-dose) vials.

Contraindications and Precautions for Vaccination

Contraindications	Precautions
Allergy to vaccine component Age <6 months Symptomatic HIV infection or CD4 T-lymphocytes <200/mm3 (or <15% of total in children aged <6 years)1 Thymus disorder associated with abnormal immune-cell function Primary immunodeficiencies Malignant neoplasms Transplantation Immunosuppressive and immunomodulatory therapies	Age 6–8 months Age ≥60 years Asymptomatic HIV infection and CD4 T-lymphocytes 200–499/mm3 (or 15%–24% of total in children aged <6 years)1 Pregnancy Breastfeeding

Adverse Reactions

• Reactions to yellow fever vaccine are generally mild and include headaches, myalgia (muscle aches), and low-grade fevers.
• There have been reports of rare but serious events following yellow fever vaccination; These events include anaphylaxis, yellow fever vaccine-associated viscerotropic disease (YEL-AVD, disease affecting certain internal organs), and yellow fever vaccine-associated neurologic disease (YEL-AND, disease affecting the nervous system).

Yellow fever vaccine–associated neurologic disease (YEL-AND)	Yellow fever vaccine–associated viscerotropic disease (YEL-AVD)
YEL-AND represents a conglomerate of different clinical syndromes, including meningoencephalitis, Guillain-Barré syndrome, acute disseminated encephalomyelitis, and rarely, bulbar and Bell palsies. Historically, YEL-AND was seen primarily among infants as encephalitis, but more recent reports have been among people of all ages. The onset of illness for documented cases is 3–28 days after vaccination, and almost all cases were in first-time vaccine recipients. YEL-AND is rarely fatal. The incidence of YEL-AND in the United States is 0.8 per 100,000 doses administered. The rate is higher in people aged ≥60 years, with a rate of 1.6 per 100,000 doses in people aged 60–69 years and 2.3 per 100,000 doses in people aged ≥70 years.	YEL-AVD is a severe illness similar to wild-type disease, with vaccine virus proliferating in multiple organs and often leading to multisystem organ failure and death. Since the initial cases of YEL-AVD were published in 2001, >60 confirmed and suspected cases have been reported throughout the world. YEL-AVD has been reported to occur only after the first dose of yellow fever vaccine; there have been no reports of YEL-AVD following booster doses. The median time from YF vaccination until symptom onset for YEL-AVD cases was 4 days (range, 0–8 days). The case-fatality ratio for all reported YEL-AVD cases worldwide is 63%. The incidence of YEL-AVD in the United States is 0.4 cases per 100,000 doses of vaccine administered. The rate is higher for people aged ≥60 years, with a rate of 1.0 per 100,000 doses in people aged 60–69 years and 2.3 per 100,000 doses in people aged ≥70 years.
Adapted from CDC

Countries with Increased Risk of Yellow Fever

Countries with risk of yellow fever virus (YFV) transmission Africa Central and South America Angola Benin Burkina Faso Burundi Cameroon Central African Republic Chad† Congo Côte d’Ivoire Democratic Republic of the Congo† Equatorial Guinea Ethiopia† Gabon Gambia Ghana Guinea Guinea-Bissau Kenya† Liberia Mali† Mauritania† Niger† Nigeria Rwanda Senegal Sierra Leone Sudan† South Sudan Togo Uganda Argentina† Bolivia† Brazil† Colombia† Ecuador† French Guiana Guyana Panama† Paraguay Peru† Suriname Trinidad and Tobago† Venezuela† †These countries are not holoendemic (only a portion of the country has risk of yellow fever transmission). Table adapted from CDC

Countries that require proof of yellow fever vaccination from all arriving travelers Angola Benin Burkina Faso Burundi Cameroon Central African Republic Congo, Repubic of the Côte d’Ivoire Democratic Republic of Congo French Guiana Gabon Ghana Guinea-Bissau Liberia Mali Niger Rwanda São Tomé and Príncipe Sierra Leone Togo Table adapted from CDC

Vector Control

Insecticides, protective clothing, and screening of houses are helpful but not always sufficient for mosquito control; people should always use an insecticide spray while in certain areas. In affected areas mosquito control methods have proven effective in decreasing the number of cases.

Use Insect Repellent

• When you go outdoors, use an EPA-registered insect repellent such as those containing DEET, picaridin, IR3535, or oil of lemon eucalyptus on exposed skin.
• Even a short time outdoors can be long enough to get a mosquito bite.

Wear Proper Clothing to Reduce Mosquito Bites

• When weather permits, wear long-sleeves, long pants and socks when outdoors.
• Mosquitoes may bite through thin clothing, so spraying clothes with repellent containing permethrin or another EPA-registered repellent will give extra protection.
• Clothing pre-treated with permethrin is commercially available.
• Mosquito repellents containing permethrin are not approved for application directly to skin.

Be Aware of Peak Mosquito Hours

• The peak biting times for many mosquito species is dusk to dawn.
• However, Aedes aegypti, one of the mosquitoes that transmits yellow fever virus, feeds during the daytime.
• Take extra care to use repellent and protective clothing during daytime as well as during the evening and early morning.
• Staying in accommodations with screened or air-conditioned rooms, particularly during peak biting times, will also reduce risk of mosquito bites.

References

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