Declines in Pediatric Pneumococcal Complicated Pneumonia Evident Following Introduction of Higher Valent Vaccines

Incidence and proportion of pediatric pneumococcal complicated pneumonia (PnCP) were observed to generally decline from pre-pneumococcal conjugate vaccine (PCV) to post-PCV periods, but accurate standardization of PnCP surveillance strategies, reporting methods, and definitions are necessary to properly evaluate the impact of a PCV program, according to a systematic review and meta-analysis published in the European Journal of Clinical Microbiology & Infectious Diseases.¹

Image Credit: © Nadzeya - stock.adobe.com

PnCP is an infrequent but potentially serious presentation of pneumococcal pneumonia that includes various clinical presentations. According to a previous review, serotypes 1, 19A, 3, 14, and 7F have been found to be predominant causes of complicated pneumococcal pneumonia. Interestingly, the disease is a common manifestation in older adults compared with younger children, but the investigators of that review found an increase in reported incidence and proportion among children since 1990.²

Once the pneumococcal conjugate vaccine (PCV13) was introduced in 2010, hospitalizations due to empyema—a common presentation of PnCP—declined to rates not seen since before the pneumococcal conjugate vaccine 7 (PCV7). Furthermore, the percentage of PnCP cases attributed to PCV7 serotypes has decreased in children from 1990 to 2013, presenting positive developments in PCV coverage and disease prevention.³

However, the epidemiology of PnCP, whether by clinical presentation, age group, or PCV program period, lacks adequate literature. Many publications have failed to extend their observations across sequential PCV program periods, although there can be difficulty in distinguishing PnCP from other presentations of pneumococcal pneumonia. The investigators sought to better understand the impact of PCV programs on PnCP incidence through a comprehensive systematic review of incidence, proportion, and serotype distribution.¹

PubMed, EMBASE, and Global Index Medicus were searched for relevant articles published between January 2001 and March 2022. After screening 1360 records, a total of 134 were included in the final analysis. The studies were conducted across 30 countries, with their designs, reported outcome measures, and diagnostic methods varying widely across them. Sixteen studies featured a pediatric population; overall, PnCP incidences tended to be higher in groups of patients who were under 5 years of age but varied across studies based on vaccination program periods and age groups.¹

Next, the authors moved to a meta-analysis of serotype distribution, which included 65 studies, 58 in pediatric and 7 in adult populations. There was a near elimination of PCV7 serotypes between the pre-PCV and post-PCV periods, whereas the percentage of PCV13nonPCV7 serotypes increased from 55.1% in the pre-PCV period to 76.5% in the transition period, remaining stable following the post-PCV period. There was a significant decrease in the percentage of PCV7 serotypes among pediatric patients, which was mostly attributed to a decline in the percentage of serotype 14.¹

Although this review was extensive and brought together outcome data from across 2 decades and 134 studies, the authors acknowledged the difficulty in providing a truly comprehensive assessment of pneumococcal incidence, proportion, and serotype distribution. A main obstacle they encountered was the lack of studies that included all those factors together. Additionally, selected studies often did not evaluate more than 1 or 2 of the 3 possible pediatric PCV immunization program periods.¹

“Together, these factors highlight the importance of improving PnCP surveillance—standardizing methods, definitions, and reporting—to better inform PCV immunization programs about PnCP pneumococcal serotype dynamics,” the study authors concluded.¹

REFERENCES

1. Fletcher MA, Okasha O, Baay m, Syrochkina M, Hayford K. Complicated pneumococcal pneumonia in the era of higher-valent pneumococcal conjugate vaccines: A systematic literature review and meta-analysis, 2021-2022. Eur J Clin Microbiol Infect Dis. 2025. Accessed Online May 20, 2025. doi:10.1007/s10096-025-05114-8

2. Fletcher MA, Schmitt HJ, Syrochkina M, et al. Pneumococcal empyema and complicated pneumonias: global trends in incidence, prevalence, and serotype epidemiology. Eur J Clin Microbiol Infect Dis. 2014;33:879-910. doi:10.1007/s10096-014-2062-6

3. Liese JG, Schoen C, van der Linden M, et al. Changes in the incidence and bacterial aetiology of paediatric parapneumonic pleural effusions/empyema in Germany, 2010–2017: a nationwide surveillance study. Clin Microbiol Infect. 2019;25(7):857-864. doi:10.1016/j.cmi.2018.10.020