Pneumococcal Vaccine May Not Prevent Invasive Disease in Kids

Laurie Barclay, MD

February 03, 2015

In children with comorbid conditions, invasive pneumococcal disease (IPD) causes higher morbidity and mortality, according to a surveillance study published online February 2 in Pediatrics. Furthermore, many cases are caused by serotypes not included in current conjugate vaccines.

"Universal use of conjugated pneumococcal vaccines has resulted in dramatic decline in vaccine-type [IPD]," write Inci Yildirim, MD, from Boston University Medical Center and School of Public Health in Massachusetts, and colleagues from the Massachusetts Department of Public Health. "However, disease is not evenly distributed, and children with underlying clinical conditions are disproportionately represented, especially among children >5 years of age."

Enhanced surveillance from 2002 through 2014 in Massachusetts allowed identification of cases of IPD among persons younger than 18 years. Parents and/or primary care clinicians provided demographic and clinical data in follow-up telephone interviews. The investigators classified underlying conditions based on the 2012 Report of the Committee on Infectious Diseases and 2013 recommendations by the Advisory Committee on Immunization Practices.

Nearly one third of all IPD cases (29.9%) had incomplete pneumococcal vaccination at the time of IPD diagnosis. More than one fifth (22.1%) of the 1052 IPD cases identified had at least one comorbid condition, with the most common comorbidities being immunocompromising diseases (32.7%) and chronic respiratory diseases (22.4%). Among children older than 5 years, about one third (35.7%) had an underlying chronic condition.

Compared with children without known comorbidities, those with comorbidities were older (median, 54.0 vs 23.0 months; P < .001). After adjustment for age, sex, year of diagnosis, and pneumococcal vaccination status, they also had higher likelihood of hospitalization (adjusted odds ratio [aOR], 2.5; 95% confidence interval [CI], 1.7 - 3.6) and case fatality (aOR, 3.7; 95% CI, 1.5 - 8.9).

"During the last 2 years of the study, 4 years after the implementation of PCV13, IPD cases among children with comorbidities were caused by either additional serotypes in PPV23 (6/12, 50%) or other serotypes that are not included in any of the vaccines (6/12; 50%)." the authors explain.

Limitations of this study include underreporting, reliance on information collected via case report forms, and lack of detailed clinical data.

"Our study found a significantly increased risk of IPD and of a fatal outcome among children with comorbidities compared with otherwise healthy children," the study authors conclude. "Serotypes that are not included in currently available conjugate vaccine are more prevalent and cause disease in such children. We need more insight into the role of PPV23 in protecting children with underlying conditions, and new strategies to provide broader coverage among children who are at highest risk for pneumococcal infection and fatal outcomes."

This study received no external funding. One coauthor has received investigator-initiated grants related to PCV Pfizer Inc and Merck Vaccines and has received honorarium for participation in Global Pneumococcal Vaccine Advisory Boards for GSK-bio, Pfizer Inc, and Merck Vaccines. The other authors have disclosed no relevant financial relationships.

Pediatrics. Published online February 2, 2015. Abstract

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