Background

Hemolytic uremic syndrome (HUS) is typically a complication of enterocolitis from Shiga toxin-producing Escherichia coli. Streptococcus pneumoniae-associated HUS (SP-HUS) is less frequent, accounting for ~5% of HUS cases in children. This study describes the epidemiology of pediatric SP-HUS in Canada.

Methods

The Canadian Immunization Monitoring Program, ACTive (IMPACT) is a national, sentinel surveillance network for vaccine-preventable diseases. It includes 12 pediatric hospitals and ~90% of tertiary care pediatric beds across Canada. All IMPACT invasive pneumococcal disease (IPD) cases from 1991-2019 were retrospectively analyzed to describe SP-HUS occurrence according to pneumococcal conjugate vaccine (PCV13) history and SP serotype. Fisher’s Exact Test compared serotype prevalence among SP-HUS and non-HUS IPD cases.

Results

From total 6,757 IPD cases, 30 SP-HUS cases (0.44%) were identified. Among SP-HUS patients with known serotypes (25/30), serotypes 3 (9/25, 36%) and 19A (32%) were more prevalent in SP-HUS cases than in non-HUS IPD cases (p<0.01).

PCV13 serotypes occurred in 88% (22/25) of SP-HUS cases, of which 77% (17/22) occurred pre-PCV13 availability. Among the 5 SP-HUS cases occurring post-PCV13, 1 was not immunized and became ill with a vaccine preventable serotype, 1 had unknown vaccine history, and 3 were vaccine failures including serotypes 3 (n=2) and 19A (n=1).

Conclusions

Two PCV13 serotypes (3, 19A) were significantly more prevalent in SP-HUS cases compared to non-HUS IPD and were identified in all vaccine failure SP-HUS cases. Future study will examine if serotypes 3 and 19A are also more prevalent among SP-HUS cases in other geographic regions and if PCV13 is less effective against these serotypes. Further research will also identify vaccine failures in non-HUS IPD cases and compare them to those of SP-HUS.