METHODS: This single-center, cross-sectional study conducted at the Paediatric Emergency Department from 1 October 2022, to 31 January 2023, included children aged 4 years and older with ARTIs symptoms and excluded those who were COVID-19 positive. B. pertussis was detected via quantitative Polymerase Chain Reaction on nasopharyngeal swabs and pertussis toxin (PT) IgG enzyme-linked immunosorbent assay.

RESULTS: Children (n = 298) with a median (Interquartile range, [IQR]) age of 6.0 (5.0, 8.0) years old were recruited, and 98% were vaccinated adequately. Two cases of B. pertussis (n = 2/298, 0.67%) were detected. Both children were also co-infected with Bordetella spp. The majority of the patients (n = 246/296, 83.1%) had low protective antibodies against pertussis (anti-PT IgG <5 IU/ml), and children 5 years and older were more likely to have lower anti-PT Ig G levels of <5 IU/ml (odds ratio 2.02 [95% CI 1.04,3.90]) compared to children 4 years old.