Assess pHUS incidence in Sweden after PCV15 replaced PCV10 in 2023, adding serotypes 3 and 19A to vaccine coverage.
Approach:
Surveillance: Researchers identified cases through nationwide surveillance and notifications from paediatric nephrology centres.
Incidence and serotypes: Annual incidence was calculated using national paediatric population data; the Swedish Public Health Authority supplied serotype data.
Key Findings:
No pHUS cases were identified in Sweden in 2025; incidence was 0 per 100,000 children.
This contrasts with substantially higher pHUS incidence during the PCV10 era, which followed an approximately 10-fold rise after PCV13 was replaced by PCV10.
Paediatric IPD also declined after PCV15 introduction, while adult IPD did not show a similar reduction.
The authors note that England’s national surveillance also recorded declining pHUS incidence after PCV7 was replaced by PCV13.
Interpretation:
The timing of the absence of pHUS cases is consistent with the hypothesis that broader serotype coverage may reduce circulation of strains associated with pHUS. The ecological findings do not establish causality.
Limitations:
The ecological design cannot demonstrate that PCV15 caused the decline.
Possible alternative explanations include natural annual variation, secular changes in pneumococcal epidemiology, and stochastic effects related to the rarity of pHUS.
Continued surveillance is needed to determine whether the absence of cases in 2025 represents a sustained trend.
Conclusion:
The authors describe the rise in pHUS during the PCV10 era and the absence of cases after PCV15 introduction as a notable natural experiment. They state that ongoing national surveillance will be essential.
