Risk factors associated with death in infants <120 days old with severe pertussis: a case-control study

Background and purpose Pertussis is a serious infectious disease in young infants, and severe cases frequently cause death. Our study explored risk factors for death from severe pertussis. Method A case-control study of infants with severe pertussis admitted to the paediatric intensive care unit (PICU) in the Children's Hospital of Chongqing Medical University, China, from January 1, 2013, to June 30, 2019, was conducted. Pertussis was confirmed by clinical features and laboratory examinations. Severe pertussis was defined as patients with pertussis resulting in PICU admission or death. To understand the risk factors for death, we compared fatal and nonfatal cases of severe pertussis in infants aged < 120 days by collecting clinical and laboratory data. Results The participants included 63 infants < 120 days of age with severe pertussis. Fifteen fatal cases were confirmed and compared with 44 nonfatal severe pertussis cases, Four patients with termination of treatment were excluded. In the univariate analysis, the risk factors associated with death included apnoea (P = 0.001), leukocytosis (white blood cell (WBC) count >= 30 x 10(9)/L (P = 0.001) or >= 50 x 10(9)/L (P = 0)), highest lymphocyte count (P = 0), pulmonary hypertension (P = 0.001), and length of PICU stay (P = 0.003). The multivariate analysis revealed that apnoea (OR 23.722, 95%CI 2.796-201.26, P = 0.004), leukocytosis (OR 63.708, 95%CI 3.574-1135.674, P = 0.005) and pulmonary hypertension (OR 26.109, 95%CI 1.800-378.809, P = 0.017) were significantly associated with death. Conclusion Leukocytosis and pulmonary hypertension exhibited the greatest associations with death in infants with severe pertussis admitted to the PICU. Vaccination is still the most effective protection method against pertussis.