Ten of 15 participants colonized after challenge with B1917 strain.
Samples from 15 participants were collected between November 2017 and September 2018. Five participants were challenged intranasally with 1 × 10To determine the colonization status after challenge, nasal washes were performed from D4 onwards as described previously (Ag-specific serum IgG levels (against PT, filamentous hemagglutinin [FHA], pertactin [Prn], and fimbriae 2 and 3 [Fim2/3]; expressed as IU/mL) were determined at baseline and on D28 (