Congenital rubella after maternal reinfection.

This report concerns a boy with congenital rubella virus infection. The diagnosis was confirmed by virus isolation, demonstration of rubella-specific serum IgM and by persistence of serum antibody at the age of 9 months. In 2 sera from the mother sampled 2 weeks apart 20 months before the birth of the boy, low titers of rubella antibody were demonstrated by hemagglutination-inhibition, hemolysis-in-gel and complement fixation tests, but not by neutralization. Significant rises in titer were demonstrable by all serologic reactions--including neutralization--at the time of birth of the infected child. The mother was not aware of any rubella-like illness or exposure to such disease during pregnancy. The case is discussed against findings of neutralizing activity in sera from natural immunes and rubella vaccinees.