YF-Vax Disease Interactions

Ideally, vaccination should occur when an individual is healthy, thus minimizing the risk of an adverse host reaction and/or vaccine failure. However, a current or recent infection does not necessarily preclude the use of vaccines, depending on the severity of the patient's symptoms and their etiology. Superficial infections and minor acute illnesses such as a mild upper respiratory infection with or without low-grade fever do not contraindicate immunization, particularly if prompt administration of a vaccine is deemed necessary or beneficial. In fact, when vaccines are administered during the course of a minor illness, the risk of adverse events is not increased, and serum antibody response is not often diminished. On the other hand, if fever or symptoms suggest a moderate or severe illness, it is usually appropriate to withhold vaccination until the patient has recovered. In addition to the potential risks already mentioned, evolving signs and symptoms of the illness can sometimes confound the diagnosis of a vaccine reaction if it develops. In the presence of any infection, the decision to administer or withhold/defer immunization should take into consideration the benefits versus the risks to an individual patient.

In general, the use of yellow fever vaccine is contraindicated in patients with primary or acquired immunodeficiency. Since yellow fever vaccine contains live attenuated virus, the absence of immune competence may potentiate the replication of vaccine virus, increase adverse host reactions, and compromise serum antibody response. In patients with severe immunosuppression or known HIV infection, the use of yellow fever vaccine may pose a theoretical risk of encephalitis. Asymptomatic HIV-infected patients may be vaccinated if potential exposure to yellow fever virus is deemed unavoidable. However, they should be monitored for adverse effects, and it may be necessary to have neutralizing antibody titers obtained before departure to gauge the adequacy of the serum antibody response. Finally, the vaccine should not be administered to anyone with a family history of congenital or hereditary immunodeficiency until the individual's immune status can be assessed and is determined to be adequate.