Trends and determinants of pertussis mortality in Sabah, Malaysia

Pertussis remains a major cause of infant morbidity and mortality despite widespread vaccination. Sabah, Malaysia, has consistently reported the nation's highest pertussis burden. This study described the epidemiology of pertussis and identified factors associated with mortality among confirmed cases in Sabah.

A retrospective registry-based study was conducted using data from the Communicable Disease Control Information System (CDCIS) for all confirmed pertussis cases reported between January 2023 and December 2024. Sociodemographic, vaccination, and clinical variables were extracted. Univariable and multiple logistic regressions were performed to determine factors associated with death; variables with p < 0.25 were entered into the multivariable model. Adjusted odds ratios (aOR) with 95 % confidence intervals (CI) were reported.

A total of 287 confirmed pertussis cases were recorded, including 35 deaths (case-fatality rate = 12.2 %). Most deaths occurred in infants < 2 months and among non- Malaysian or unvaccinated children. In the multivariable model, shortness of breath (aOR = 21.6; p < 0.001), cyanosis (aOR = 5.45; p = 0.006), fitting (aOR = 14.2; p = 0.027), and post-tussive vomiting (aOR = 136.0; p = 0.004) were independent predictors of death. Male sex was protective (aOR = 0.23; p = 0.008). Age, citizenship, and vaccination status were not statistically significant after adjustment. The model demonstrated good fit (Hosmer-Lemeshow p = 0.807; Nagelkerke R² = 0.471).

Pertussis mortality in Sabah remains high and is driven primarily by severe clinical manifestations, with additional influence from demographic and structural factors. Strengthening early clinical recognition, improving referral and intensive care capacity, and expanding preventive strategies particularly maternal vaccination and equitable immunisation for non-Malaysian populations are critical to reducing preventable deaths.