Prevalence of anti-group B streptococcal type III capsular IgG antibodies in the United Kingdom and an analysis of their specific IgG subclasses.

Neonatal infection due to group B streptococcus (GBS) has a higher incidence in the USA than in the United Kingdom. A British population was investigated to ascertain the proportion of women who have protective anti-GBS type III IgG levels. Thirty-one (34%) of 90 pregnant women, 10 (43%) of 23 nonpregnant women, and 5 (50%) of 10 mothers of healthy colonized infants had anti-type III IgG greater than or equal to 2 micrograms/ml. Of 19 mothers who had infants infected with GBS type III, 17 (89%) had low specific IgG levels; of the other 2, the infants themselves had low IgG levels. The proportion of women in the UK with protective antibody levels is higher than in the USA. Sera (12) were assayed for anti-type III IgG isotypes; all contained IgG2, 6 had detectable IgG1, and 1 had IgG4.