Association between pertactin-producing Bordetella pertussis and fulminant pertussis in infants: a multicenter study in France, 2008-2019.

Virulence factors of the causative agent, Bordetella pertussis, may be involved in fulminant pertussis, the most severe form of whooping cough (pertussis) in infants. We aimed to assess the association between fulminant pertussis and the status of pertactin (PRN) production of B. pertussis clinical isolates. Symptomatic infants aged <6 months and with a positive B. pertussis culture from 2008-2019 were included. B. pertussis isolates and clinical data were collected from French hospital laboratories through the national pertussis surveillance network. Fulminant pertussis was defined as a case with a leukocyte count > 40 x 10 We included 361 infants with pertussis (median age 63 days [interquartile range, 39-86]), of which 32 (9%) progressed to fulminant pertussis. None of the mothers was vaccinated during pregnancy. Of the 361 implicated B. pertussis isolates, 294 (81%) produced PRN. Patients with fulminant pertussis were more often neonates (adjusted relative risk [aRR] 3.62, 95% confidence interval [CI] 1.76-7.44), infants with a history of prematurity (aRR 7.08, 95%CI 3.06-16.36), unvaccinated infants (aRR 4.42, 95%CI 1.02-19.24), and infants infected by PRN-producing isolates (aRR 3.76, 95%CI 1.02-13.83). PRN-producing B. pertussis was independently associated with an increased risk of fulminant pertussis. In a context where PRN-containing aP vaccines favor the emergence of PRN-deficient isolates, our study suggests a positive role for such vaccines in driving the evolution of B. pertussis populations towards reduced virulence.

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Conflicts of interest statement The authors did not declare any conflict of interest.