-associated hemolytic uremic syndrome Canadian Immunization Monitoring Program ACTive National Pediatric Surveillance (1991 to 2019).

Objectives: -associated hemolytic uremic syndrome (SP-HUS) is an underreported cause of pediatric atypical HUS. This study describes the epidemiology of the largest Canadian case series of SP-HUS in comparison with non-HUS invasive pneumococcal disease (IPD).

Methods: The Canadian Immunization Monitoring Program, ACTive (IMPACT) is a national surveillance network for vaccine-preventable diseases. All confirmed IPD cases from 1991 through 2019 were included in the analysis. IPD cases with new HUS diagnoses were identified as SPHUS cases, and the rest as non-HUS IPD.

Results: There were 30 (0.4%) cases of SP-HUS amongst 6757 IPD cases. The median age of SP-HUS cases was 27.5 months, with no significant differences between SP-HUS and non-HUS cases in age or sex. serotypes 3 (30%) and 19A (26.7%) were more common in SP-HUS compared to non-HUS (P < 0.0001). Pneumonia was more frequently observed in SPHUS than in non-HUS (67% versus 26%; P < 0.0001). All SP-HUS cases were hospitalized, compared with 71% of non-HUS IPD cases (P = 0.0004). SP-HUS cases had a longer median hospital length of stay than non-HUS (23.5 versus 7 days; P < 0.0001) and a higher proportion required an Intensive Care Unit (ICU) admission (70% versus 15.5%; P < 0.0001). Moreover, ICU stays were longer in HUS cases compared with non-HUS cases (9 versus 3 days; P < 0.0001). All 30 SP-HUS patients survived while 3% of non-HUS cases died (P = 0.33).

Conclusions: SP-HUS was usually seen in IPD cases with pneumonia and was most commonly caused by serotypes 3 and 19A. ICU care was lengthy, hospital stay was longer. No deaths occurred among SP-HUS cases.