Yellow Fever Vaccine Information

  

Indications                                                  

Disease risk for travellers

Certificate requirements under International Health Regulations

Availability

Contraindications

Precautions

Adverse events

References

Indications

Yellow fever (YF) vaccination may be recommended for protection of travellers to all countries in the endemic zones for YF, whether or not an international certificate is required under World Health Organization (WHO) International Health Regulations.

'Endemic' zones include countries (or areas within countries) where there is the potential for human infection because of the presence of YF virus in mosquitoes and non-human primates. In endemic regions human cases of YF may be occurring but are below the level of surveillance detection and are not reported to the WHO. Because of the possibility of acquiring disease during travel to endemic countries, vaccination against YF may be recommended, particularly for those who visit rural areas. In some cases vaccination may be mandatory.

Both WHO and the US Centers for Disease Control and Prevention (CDC) had used the designation: countries 'infected' with YF. In these situations, infected countries were reporting human cases of YF. WHO and CDC no longer make the distinction between endemic and infected countries; all areas considered a risk for YF are called endemic. WHO will continue to list in the Weekly Epidemiological Record cases of YF that are reported to them.  

Disease risk for travellers

In consultation with WHO and the Pan American Health Organization (PAHO), scientists at CDC have undertaken to more clearly define the endemic zones according to up-to-date epidemiological data (http://www2.ncid.cdc.gov/travel/yb/utils/ybGet.asp?section=dis

&obj=yellowfever.htm). This has resulted in the revision of their yellow fever endemic zone maps. For most countries, CDC and WHO recommendations for disease risk are the same; for a few countries they differ slightly. NaTHNaC feel that the CDC maps provide the most accurate information from which to advise the traveller about risk. 

Certificate requirements under International Health Regulations (IHRs)

The requirements for vaccination provided by each country in order to comply with IHRs have not changed. The WHO country listings should be consulted.

Availability

There are currently two yellow fever vaccines licensed for use in the United Kingdom. These use the 17D strain of yellow fever virus.

The Summary of Product Characteristics (SPC) for the individual vaccine should be consulted for specific information relating to the product.

Vaccine	Manufacturer/ Distributor	Schedule	Length of Protection	Age range
Arilvax	Not currently available
Stamaril	Sanofi Pasteur MSD	1 dose	10 years	Minimum age 9 months. Seek medical advice for infants 6-9 months who are travelling to high risk areas

 

The vaccine induces a rapid immune response with 90% of recipients achieving protective levels of antibody within 10 days. Immunity following vaccination has been shown to be long lasting and possibly life long. However, IHRs require re-vaccination at 10-year intervals if indicated, in order to retain a valid certificate and prevent the importation of yellow fever virus into susceptible countries.

Contraindications

(specific contraindications should be reviewed in the SPC)

• Age five months and under
• Persons known to be hypersensitive to any component of the vaccine including anaphylaxis to egg protein
• Immunocompromised hosts
• Thymus disorder, including myasthenia gravis, thymoma, thymectomy and DiGeorge syndrome [1]

Precautions

(Expert advise should be sought prior to immunizing individuals in these groups)

• Infants aged 6 to 8 months
• Febrile illness
• HIV-infected individuals
• Pregnant women
• Breast feeding women
• Individuals age 60 years and older

Adverse Events

The 17D strain virus yellow fever vaccine has been in use for more than 50 years and has an excellent safety profile. It has been estimated that 300-400 million doses of the vaccine have been administered worldwide [2]. Reactions to YF vaccine are usually mild and short lived. They include myalgia, headache, and low-grade fever, typically occur during the first 5-10 days post vaccination, and will affect 10-30% of recipients.

Serious adverse events are rare but have been reported and fall into three main categories: hypersensitivity reactions, vaccine-associated neurologic disease and vaccine-associated viscerotropic disease.

Hypersensitivity reactions

The vaccine is propagated in chick embryos. Vaccine stabilizers include beef gelatin and sorbitol. Anaphylaxis and urticaria as a result of sensitivity to either egg or other vaccine components, occurs at an incidence between 1:130,000 and 1:250,000 doses administered [3].

Vaccine-Associated Neurologic Disease

Post-vaccine encephalitis has been recognised as a rare event since the early use of the vaccine.  It was particularly seen in infants with early reports with an incidence of 0.5 to 4 cases per 1,000 infants under the age of 6 months [4]. Since 2001, a new pattern of neurologic adverse events has been recognized [5,6]. These events have now been termed YF vaccine-associated neurologic disease. The clinical presentation of neurologic events begins 4 to 23 days following receipt of vaccine, with fever and headache that may progress to include one or more of confusion, focal neurologic deficits, coma and Guillain Barré syndrome. The clinical course is usually complete recovery.  All cases have occurred in primary vaccinees who have no underlying yellow fever immunity.  The risk for these events is higher in older individuals.

Vaccine-Associated Viscerotropic Disease

Yellow fever vaccine-associated viscerotropic disease is a syndrome of fever and multi-organ failure that resembles severe yellow fever disease; it was first described in 2001 [7-9].  Two to 8 days following vaccination patients develop fever, malaise, headache and myalgias that progress to hepatitis, hypotension and multi-organ failure; death has occurred in more than 60% of reported cases. As with neurologic disease, all cases have occurred in primary vaccinees. In the reports of viscerotropic disease, 14% have a history of thymus disease with subsequent thymectomy [1].  All patients with thymus disorders should not receive vaccine.

Based on reported cases and the number of doses of YEL distributed, the U.S. has estimated the risk of neurologic disease to be about 5 cases per million doses and viscerotropic disease to be 4 cases per million doses [10].  These estimates are similar to those made based on cases reported in Europe [6].

For individuals who are aged 60 years and older, the current risk for neurologic and viscerotropic adverse events increases by several fold, such that neurologic events occur at a rate of about 18 cases per million doses and viscerotropic events at a rate of 22 cases per million doses [11].

The emergence of these two patterns of serious adverse events associated with YF vaccine is not felt to be secondary to alterations in the vaccine.

References

1.Barwick R. History of thymoma and yellow fever vaccine. Lancet 2004, September 11; 364:936

2. World Health Organization, Yellow Fever Vaccine, Weekly epidemiological record 2003, 78, 349-360

3. Kelso JM, Mottrey GT, Tsai TF. Anaphylaxis from yellow fever vaccine, J Allergy Clin Immunol 1999; 103:698-701.

4. Monath TP. Yellow fever vaccine. In: Vaccines.  S.A. Plotkin and W.A. Orenstien, Editors. 2004, Saunders: Philadelphia. p. 1095-1176.

5. Centers for Disease Control and Prevention. Adverse events associated with 17D-derived yellow fever vaccination - United States, 2001-2002.  MMWR 2002;51:989-993.

6. Kitchener S. Viscerotropic and neurotropic disease following vaccination with the 17D yellow fever vaccine, ARILVAX((R)).  Vaccine 2004;22:2103-5.

7. Chan RC, Penney DJ, Little D, et al. Hepatitis and death following vaccination with 17D-204 yellow fever vaccine.  Lancet 2001;358:121-122.

8. Martin M, Tsai TF, Cropp B, et al. Fever and multisystem organ failure associated with 17D-204 yellow fever vaccination: a report of four cases.  Lancet 2001;358:98-104.

9. Vasconcelos PF, Luna EJ, Galler R, et al. Serious adverse events associated with yellow fever 17DD vaccine in Brazil: a report of two cases.  Lancet 2001;358:91-97.

10. Cetron MS, Marfin AA, Julian KG, et al. Yellow fever vaccine. Recommendations of the Advisory Committee on Immunization Practices (ACIP).  MMWR 2002;51 (No. RR-17):1-10.

11. Khromava AY, Eidex RB, Weld LH, et al. Yellow fever vaccine: an updated assessment of advanced age as a risk factor for serious adverse events. Vaccine 2005; 23:3256-63.