Relevance of age at diagnosis to prevention of late-onset group B streptococcal disease by maternal immunization.

Among 248 infants with late-onset group B streptococcal (GBS) disease from 1993 to 2012, approximately two thirds (63%) had a gestation of at least 35 weeks and 72% of these became ill within 6 weeks of life (median 27 days), suggesting that third trimester maternal GBS immunization could substantially reduce the late-onset GBS disease burden in the United States.