Critical pertussis infection in the paediatric intensive care unit: A case series in an outbreak.

Background: Bordetella pertussis is a highly infectious disease associated with increased mortality in young infants. Critical pertussis is defined as pertussis disease resulting in paediatric intensive care unit admission or death.

Objectives: This study describes the clinical profile, morbidity, mortality and management of children with critical pertussis admitted to a South African paediatric intensive care unit (PICU).

Study design: A retrospective analysis of children with critical pertussis admitted to the PICU over 1 year (January 2022 - December 2022).

Results: There were 1 273 PICU admissions during the study period, of which 101 (7.9%) were tested and 19 (1.5%) tested positive for B. pertussis. Of those, 13 (68.4%) were completely unimmunised, mainly owing to young age (n=9). The median (interquartile range) total duration of ventilation was 7.0 (3.0 - 21.0) days, with a maximum of 35 days. Mortality was 36.8% (n=7) in those with B. pertussis; with more deaths in HIV-exposed patients (n=3/7,42.9% v. n=3/12, 25%; p<0.001) and preterm infants (n=4/7,57.1% v. n=4/12, 33.3%; p<0.001), as well as those with septic shock (n=7/7, 100% v. n=4/7, 33.3%; p = 0.02) and acute kidney injury (n=6/7, 85.7% v. n=2/12, 16.7%; p<0.001). The maximum white cell count was significantly lower in survivors (27.75 v. 76.32; p<0.001). None of the variables was independently associated with mortality on multivariable regression.

Conclusion: Critical B. pertussis infection is associated with significant morbidity and mortality in this setting. The low rate of vaccination is a concern, and advocacy is needed to promote access to vaccination during the third trimester of pregnancy as well as strengthening current immunisation programmes. Further research is required to identify the prevalence of critical pertussis and risk factors for poor outcomes in resource-limited settings.

Contribution of the study: This study demonstrated high mortality rates in infants with critical pertussis under the age of 3 months, especially in infants who are unimmunized or partially immunized. We therefore recommend vaccination against Bordetella pertussis in the third trimester of pregnancy and stress the importance of strengthening current immunization programmes. Our study highlights the importance of describing the markers of disease severity, such as hyperleukocytosis, especially in resource constrained settings, in order to ensure timeous transfer to PICU. We recommend further research regarding these markers of disease severity as well as therapies offered such as leukoreduction or exchange transfusion.