Incidence and Clinical Severity of Pertussis in Children after the COVID-19 Pandemic: A Comparative Study of Unvaccinated and Partially Vaccinated Patients

Abstract

Background: Pertussis remains a serious bacterial infection in children, especially infants, despite routine vaccination. During the COVID-19 pandemic, reported cases declined due to public health restrictions, but routine immunization coverage was disrupted as well. In the post-pandemic period, a resurgence of pertussis has been observed globally, including in Georgia. Evaluating disease frequency and clinical severity in children is essential for understanding current trends and improving prevention strategies. Objectives: This study aimed to evaluate the incidence and clinical severity of pertussis in children after the COVID-19 pandemic and to compare disease occurrence and severity between unvaccinated and partially vaccinated groups. Methods: This retrospective study (Jan 2024–Jan 2025) included 66 hospitalized and 34 outpatient children with PCR- or serology-confirmed pertussis from two pediatric clinics in Georgia. Results: Unvaccinated patients had higher rates of prolonged cough (>10 days: outpatients 83%, hospitalized 74%), paroxysmal cough (outpatients 92%, hospitalized 55%), pneumonia (outpatients 58%, hospitalized 84%), and leukocytosis (>10×10⁹/L: outpatients 58%, hospitalized 63%; >20×10⁹/L: hospitalized 29% vs 15% in partially vaccinated) compared with partially vaccinated patients. Vomiting after coughing was more frequent in partially vaccinated outpatients (86%) but higher in unvaccinated hospitalized patients (82%), while normal leukocyte counts, nighttime cough, and brief loss of consciousness were more common or similar in partially vaccinated children. Conclusions: Unvaccinated children had more severe pertussis, underscoring the role of vaccination in the post-pandemic period.