enhanced respiratory syncytial virus disease
enhanced respiratory syncytial virus diseaseAn altered form of measles—atypical measles syndrome (AMS)—with an abrupt onset of high fever, headache, cough, and abdominal pain. The rash may appear 1 to 2 days later, often beginning on the limbs. Swelling (oedema) of the hands and feet may occur. Pneumonia is common and may persist for 3 months or more.
AMS occurs in persons who were incompletely immunised against measles. This may happen if a person was given the old killed-virus measles vaccine (which does not provide complete immunity and is no longer available), or the person was given attenuated (weakened) live measles vaccine that was, by accident, inactivated during improper storage. Immunisation with inactivated measles virus does not prevent measles virus infection. It can, however, sensitise a person so that the expression of the disease is altered, resulting in AMS.
Atypical measles syndrome (AMS) and enhanced respiratory syncytial virus disease were serious diseases that resulted from exposure of children immunised with inactivated vaccines against measles virus (MV) and respiratory syncytial virus (RSV) to the respective wild-type agents in the 1960s. Although the clinical manifestations of both illnesses were different, the immune responses elicited and primed for by the vaccines shared important similarities. Both vaccines failed to elicit long-lived protective antibody and to promote cytotoxic T lymphocyte responses, and in both cases, post-vaccination exposure to wild-type virus during community outbreaks was associated with immune complex deposition in affected tissues, vigorous CD4+ T lymphocyte proliferative responses and a Th2 bias of the immune response. No relapses of atypical measles or ERD were ever reported.