Difficulties in interpretation of rubella serology

Detection of rubella-specific IgM in subclinical rubella reinfection in pregnancy

Seven cases of asymptomatic rubella reinfection in early pregnancy are described. In each, there was a history of exposure to a rubelliform illness and low levels of rubella-specific IgM subsequently appeared in the serum. Four of the women had been immunised, after having been shown to be susceptible to rubella, one had been immunised at school without previous antibody screening, and two were uncertain about immunisation. One pregnancy was terminated and rubella virus was not isolated from the products of conception. Six pregnancies went to term and the infants showed no evidence of intrauterine infection. In a further case it was impossible to discriminate between reinfection and primary infection, and termination of pregnancy was offered.

Clinically apparent rubella reinfection

We report two cases of rubella reinfection in apparently immunocompetent young women. In both cases rubella-specific IgG had been detected on two occasions prior to an illness clinically diagnosed as rubella. Rubella-specific IgM was detected by various techniques in samples of serum collected at the time of the illness.