Late Breaking Abstract - Pertussis incidence among older adults with asthma and COPD in South Korea

Abstract

<b>Background:</b> Incidence of pertussis in older adults in South Korea may be underestimated due to atypical clinical presentation and underreporting to the Korea Disease Control and Prevention Agency (KDCA) surveillance system. <b>Aim:</b> Assess the incidence of pertussis in adults ≥50 years in South Korea with and without asthma or chronic obstructive pulmonary disease (COPD). <b>Methods:</b> This retrospective cohort study used the nationwide Health Insurance Review and Assessment service (HIRA) database to identify patients ≥50 years diagnosed with pertussis (ICD-10 code: A37) from 2009–‍2018. We calculated disease incidence rates (IRs) per 100,000 persons and incidence rate ratios (IRRs) in patients&nbsp;with asthma or COPD in the year before diagnosis versus (vs) those without. The historical control group was defined&nbsp;from the HIRA-National Patient Sample cohort (3% of persons representative of the entire South Korean population). <b>Results:</b> This study identified 1,011 patients diagnosed with pertussis from 2009–2018 in the HIRA database vs 358 reported to the KDCA. Of these, 175 had asthma, 96 had COPD (groups not mutually exclusive), and 796 had neither. Overall IRs of pertussis were highest in asthma (mean IRs [95% CI]: 3.4 [1.8–4.9]), followed by COPD patients (2.5 [0.9–4.0]) vs those with neither (0.5 [0.4–0.6]). IRs increased over time, especially for asthma/COPD patients. Overall IRRs relative to patients without asthma/COPD (95% CI) were higher for asthma (6.7 [5.7–7.9]) than for COPD patients (4.9 [4.0–‍6.1]). <b>Conclusion:</b> The highest incidence of pertussis was observed in asthma, followed by COPD patients vs those without. Over twice as many patients than reported to the KDCA were identified, highlighting underreporting.