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Over 500million people live in yellow fever (YF) endemic areas and more than 3million travel to endemic countries every year. Prevention against YF, caused by the YF virus, an arbovirus, can only be efficiently obtained by active immunization. The vaccine is well tolerated and severe adverse events are very rare. Exceptionally, YF vaccination may result in serious adverse events, such as viscerotropic and neurotropic diseases, sometimes with a fatal outcome. These rare serious adverse advents are reviewed with their potential risk factors, such as advanced age or history of thymus disease. The benefit/risk ratio remains in favour of vaccination, although the decision to offer yellow fever vaccination, especially to persons 60years of age or older, should be evaluated according to the planned trip. Additional research investigations should be made on the host immune response since this response is considered to be at the origin of these severe adverse events.

Yellow fever vaccine (17D, a live attenuated virus vaccine) was effective and safe in 2 human immunodeficiency virus-infected patients without severe immunosuppression, one of whom traveled to Kenya and the other of whom traveled to Senegal.

Simultaneous vaccination against hepatitis A and yellow fever has been studied in our unit: Santé-Voyage, Bordeaux. This randomised study included 108 healthy subjects: 36 received hepatitis A vaccine (Havrix, SKF), 36 received yellow fever vaccine and 36 received both. For hepatitis A vaccine protocol comprised one injection at day zero, one at D15, and one booster dose at 6 months. Those who received yellow fever vaccine had it at D0. Simultaneous vaccination is well tolerated and immunogenicity is as good as it is for each vaccine separately. This is particularly interesting for tropical travellers who are at risk for hepatitis A.

Abstract: Any person travelling in countries where yellow fever (YF) is endemic and without presenting contra-indication for the vaccination against YF may be vaccinated. This vaccination can very rarely induce a potentially lethal neurotropic or viscerotropic disease. In severely immunodeficient patients, the vaccination is contra-indicated because postvaccinal encephalitis may occur after the vaccination, due to vaccine strain pathogenecity. It is important to evaluate the general health status in elderly individuals before vaccinating because of the increased risk of viscerotropic disease in people of 60 years of age and over. Pregnant women should not be vaccinated, except if departure to an endemic zone is unavoidable. YF vaccination is contra-indicated for newborns under six months of age. Solid organ grafts, congenital immunodeficiency, leukemia, lymphoma, cancer, and immunosuppressive treatments are contra-indications for this vaccination. Nevertheless, YF immunization is possible after a bone marrow graft and a two-year period without graft-versus-host disease or immunosuppressive treatment. There is no data to support that immunization of the donor prior to the graft could confer protection against yellow fever to the recipient. Low doses, short courses of corticosteroids either as systemic treatment or intra-articular injections are not contra-indications for YF vaccination. Patients infected with HIV with stable clinical status and T CD4-cell count above 200 cells per millimetre cube may be vaccinated. Thymic diseases, including thymoma and thymectomy, are contra-indications for YF vaccination. Finally, a substantial residual level of antibodies beyond 10 years after the latest vaccination could confer protection, thus avoiding a new vaccination when it is an issue. [Copyright &y& Elsevier]