The evolving epidemiology of paediatric acute mastoiditis in New Zealand.

BACKGROUND

In 2017, PCV-13 was replaced by PCV-10 in the New Zealand immunisation schedule. The aim of this study was to evaluate the impact of this change on the incidence and microbiology of paediatric acute mastoiditis (AM) in NZ.

METHODS

A retrospective observational study was conducted, including patients aged <18 years with an ICD-10 diagnosis of AM documented in the NZ National Minimum Dataset between 2014 and 2022. Clinical and microbiological data were obtained for a sub-group of cases admitted to five tertiary hospitals across NZ. Cases were divided into four periods, 2014-2016 (PCV-13 baseline), 2017-2019 (transition), 2020-2021 (PCV-10 COVID) and 2022 (PCV-10 post-COVID) for analysis. In each period the national incidence of all-cause AM, proportion of AM cases attributable to S.pneumoniae and proportion of S.pneumoniae AM cases presenting with a subperiosteal abscess were compared with the baseline period.

SUMMARY OF

RESULTS

391 new cases of paediatric AM occurred during the study period. The national incidence of paediatric AM increased from a baseline of 3.62 cases/100,000 person-years in 2014-2016 to 6.22 cases/100,000 person-years in 2022 (RR 1.72, 95 % CI 1.28-2.30). Microbiological data was available for 212 cases. In 2022 48 % of cases were attributed to S.pneumoniae, compared with 27 % in the baseline period (p = 0.03). In 2022 17/20 (85 %) of S.pneumoniae cases presented with a sub-periosteal abscess, compared with 8/18 (44 %) in the baseline period (p < 0.01).

CONCLUSION

The national incidence in NZ of all-cause paediatric AM increased in 2022, with a significant increase in the proportion of cases attributable to S.pneumoniae.