Placental transfer of maternal rubella antibodies to full-term and preterm infants.

Premature infants are vulnerable to infections, partly because of the low transplacental transfer of maternal antibodies. The present study investigated the placental transfer of maternal rubella-specific antibodies to full-term and preterm infants. The study group consisted of 133 healthy, native Israeli mothers and their 159 newborns. Of these, 69 were full-term infants (gestational age > 37 weeks) of 69 mothers, and 90 were preterm infants (gestational age < 35 weeks) of 64 mothers. Antibody titers against rubella were measured in maternal and umbilical cord blood samples by hemagglutination inhibition and microneutralization techniques. There was no significant difference in the level of protection and in geometrical mean titers by hemagglutination between the full-term and preterm groups. Conversely, significant differences in geometric mean titers of neutralizing antibodies were found between full-term and preterm infants, e.g., 65.9 and 39.8, respectively (P < 0.001). Very low birth weight preterm infants are at greater risk of rubella infection during the first year of life, due to the diminished transfer of neutralizing maternal antibodies. Therefore, earlier vaccination of this group may be beneficial.

Rubella in pregnancy in Israel: 15 years of follow-up and remaining problems.

Despite extensive vaccination programs introduced in Israel since 1973, rubella virus continues to pose a threat to pregnant women. Screening for antibodies from women of childbearing age between 1980 and 1994 showed a decrease in seronegativity from 15.4% to 7% between the years 1980 and 1988, followed by an increase to 9.6% in 1991-92 due in part to the large wave of immigration from the former USSR, and a decrease back to 6.9% in 1993-94. The morbidity fluctuated, with peaks in 1983, 1987 and 1991, yielding a total of 219 cases in the target population of women of childbearing age. Additional problems encountered were reinfections, vaccine failures, and false positive results in screening. During the study period we confirmed 35 cases of reinfections in pregnancy, 19 of which resulted in delivery of healthy babies. In two of four cases of abortion following reinfection that we could follow, the fetus was infected. Immunization of 15-month-old babies introduced in 1989 and the new policy of two-dose vaccination introduced in 1995 are expected to further reduce the spread of rubella virus in the coming years.

Detection of rubella-specific IgM antibodies by the staphylococcal absorption method (SAM).

The use of SAM for the detection of rubella-specific IgM was evaluated in the sera of 318 rubella convalescents, 79 vaccinees and 53 infants with congenital rubella syndrome (CRS). The method employed was based on the use of crude inactivated suspension of Staphylococcus aureus strain Cowan I in the hemagglutination inhibition (HI) test and 1-h incubation of antigen and antibody. Among convalescents, 99% were found positive when tested within 30 days, and 84.6% were positive within 90 days following onset of clinical symptoms. Infants with CRS were 50 to 55% positive at the age of 0 to 6 months and 23% at the age of 7 to 11 months. Overnight incubation of antigen and antibody increased the proportion of positive results, particularly among sera of rubella vaccinees. No false-positives were detected among 1,035 healthy controls; nor in 40 patients following cytomegalovirus or Epstein-Barr virus infection, nor in 22 sera containing rheumatoid factor (RF). Comparison of SAM with a commercial enzyme-linked immunosorbent assay (ELISA) kit based on antibody capture showed 84% correlation between the two methods. Discrepancies were observed mainly in low-IgM.antibody-containing sera.