Clinical Significance

Rubella is a viral exanthematous, infectious disease that typically follows a benign clinical course. Symptomatology is generally characterized by fever, with maculopapular rash accompanied by enlargement of lymph nodes .
Widespread vaccination of children has greatly reduced the incidence of rubella in the general population. However, total eradication of rubella in the population is unlikely. Because many rash illnesses mimic rubella and because many rubella infections are asymptomatic, rubella can often be overlooked or misdiagnosed .
By far, the greatest consequence of rubella is Congenital Rubella Syndrome (CRS), which could cause miscarriages, stillbirths, fetal abnormalities, and therapeutic abortions as a result of infection in early pregnancy, especially in the first trimester. Fetal abnormalities may be hepatosplenomegaly, psychomotor retardation, bone alterations, cardiopathies, or neuropathies. Pathological consequences to the fetus depend on the virus teratogenic potency and on when the infection is contracted during pregnancy. The consequences to the fetus are highest in cases of rubella infection during the first two months of pregnancy, but decrease progressively if infection occurs at the 4th or 5th month . The risk of severe neonatal complication points to the need for accurate methods to determine the immune status of women of childbearing age.
Reinfection can occur following either naturally acquired or vaccine-induced immunity, but is much more likely to occur in the latter. Reinfection is almost always subclinical and is defined by a rise in preexisting antibody. Viremia and systemic manifestation are uncommon. The risk of fetal transmission and subsequent CRS resulting from maternal reinfection during pregnancy is low .
Since the availability of the vaccine in the late 1960s, the assay of rubella IgG has been widely used to determine the immune status, to determine the need for vaccination and to evaluate vaccine efficacy and screening for rubella virus is now generally performed by immunoassay . Specific IgG antibodies generally appear several weeks postinfection; reach their maximum concentration and then progressively decrease to a low level persisting for life.
Rubella vaccines will induce the production of IgG antibodies similar to that observed with natural infection. However, antibody titers following vaccination may be delayed and somewhat lower than the titers observed with natural infections .