Post-pandemic increase in pediatric invasive pneumococcal disease driven by serotype 3.

BACKGROUND

Invasive pneumococcal disease (IPD) remains a significant cause of morbidity in children despite widespread use of conjugate vaccines. The COVID-19 pandemic led to unprecedented changes in respiratory pathogen circulation and pediatric infectious disease epidemiology.

MATERIALS AND

METHODS

We conducted a retrospective study of children under 18 years admitted with confirmed IPD to a tertiary hospital in Madrid, Spain (January 2018-April 2023). Clinical, microbiological, and vaccination data were analyzed, with comparisons by disease severity and pre-/post-pandemic period (March 15, 2020).

RESULTS

A total of 38 children were included (median age 27 months). Most (76.3 %) had no recognized risk factors for IPD. Pneumonia was the most frequent presentation (47.4 %), and 57.9 % met severity criteria. A marked decline in IPD occurred during the early COVID-19 pandemic (March 2020-August 2021), with no confirmed cases during that period. However, incidence and severity rose from late 2022. Severe cases were significantly more frequent post-pandemic (42.1 % vs. 73.7 %, p = 0.049). Fourteen patients (36.8 %) required PICU admission; one death (2.6 %) occurred in a previously healthy, fully vaccinated child with serotype 3 meningitis. Serotype 3 was most common (23.7 %) and strongly linked to severity (40.9 % of severe cases), occurring in fully vaccinated children in 88.9 % of cases.

CONCLUSIONS

Following COVID-19, a resurgence in pediatric IPD was observed, largely driven by serotype 3. This serotype was linked to greater severity, PICU admissions, and one fatal outcome, despite high PCV13 coverage. These findings underscore the need for improved vaccine formulations, sustained surveillance, and timely adaptation of immunization strategies.