Methods: Healthy 7-to-17-year-old children with cough lasting from 2 to 8 weeks were enrolled. Excluded were the patients who had received the pre-school booster (PSB) PT vaccine less than one year before the cough onset. At enrolment, a nasopharyngeal swab and an oral fluid sample were obtained to seek pertussis infection by detection of B. pertussis DNA in the nasopharynx using PCR and/or an elevated titer of anti-pertussis toxin IgG in oral fluid using an IgG antibody-capture enzyme-linked immunosorbent assay. Saliva determination of anti-PT toxin IgG was used because it acts as a surrogate for anti-PT toxin IgG serology.
Results: Among 96 patients, pertussis was diagnosed in 18 (18.7%; 95% CI 11.5 - 28.0). In 2 children with cough lasting 2 weeks, confirmation was based on the detection of B. pertussis; in 13 cases, with cough lasting 4-7 weeks, PT was diagnosed because there were high anti-PT IgG titers in oral fluid; and in 3 cases, with cough lasting 3 weeks, PT was diagnosed due to positivity for both tests. In 15 children, the disease occurred despite PSB administration. In 2 cases, PT diagnosis was made only 16 and19 months after booster injection, whereas in other 13 cases infection emerged after a longer period. However, in eight cases disease occurred less than 5 years after vaccine administration.
Conclusion: This study demonstrates that about 20% of persistent cough in children is due to PT. In case of persistent cough, this has to be considered to prescribe an effective therapy. Moreover, the study confirms that protection evoked by PT vaccine rapidly wanes and that schoolchildren may return to be PT susceptible after few year of the officially recommended PSB dose. If confirmed, these findings might lead to anticipate presently recommended PT vaccine dose for adolescents.
L. Terranova, None
M. Picca, None
C. Malvaso, None
C. Vitale, None
N. Fry, None
S. Esposito, None