Outpatient CAP rates remain stable, despite vaccination

Kronman MP. Pediatrics. 2011;doi:10.1542/peds.2010-2008.

The rate of children who were hospitalized for community-acquired pneumonia did not change significantly between the 1990s and during the past decade, despite introduction of the heptavalent pneumococcal conjugate vaccine in 2000, according to research from the National Ambulatory and National Hospital Ambulatory Medical Care Surveys.

The surveys also revealed that macrolides were frequently prescribed despite evidence that they provide little benefit over penicillins.

Matthew P. Kronman, MD, of the division of infectious diseases and division of general pediatrics, The Children’s Hospital of Philadelphia, and colleagues used the surveys to identify children with community-acquired pneumonia (CAP). They looked at outpatient CAP rates and data surrounding broad-spectrum antibiotic use to treat the patients.

CAP visit rates ranged from 16.9 to 22.4 per 1,000 population, with the highest rates occurring in children younger than 5 years, with no variation after 2000, despite routine use of the 7-valent pneumococcal conjugate vaccine (Prevnar, Wyeth). The researchers said the vaccine may be preventing more serious cases of Streptococcus pneumoniae, but not some of the milder cases. This may explain another trend noted in the findings; notably, that from 2000 to 2007, there was about an 8% decrease in emergency visits, but a corresponding 8% increase in office visits related to S. pneumonia.

Physicians commonly prescribed broad-spectrum antibiotics, including macrolides and cephalosporins. Penicillins were prescribed less frequently, about 14%, compared with the other antibiotics. The researchers said cephalosporin use increased significantly in the years after vaccine introduction. Increasing age, a visit to a nonemergency department office, and obtaining a radiograph or complete blood count were all predictive of broad-spectrum antibiotic prescribing.

The researchers said there were some limitations, including that the survey data did not include information on allergies or physical exam findings. Also, some of the cases may have been viral infections, not CAP.

Disclosure: The researchers reported no relevant financial disclosures.

This large cross-sectional study utilizes a national database of pediatric hospital discharges representing approximately 89% of the estimated US population. Thus it offers a clear picture of trends in the rates of hospitalization of previously healthy children aged 18 years and younger with community acquired pneumonia (CAP) and its local and systemic complications in 3-year intervals from 1997, 3 years before the introduction of the seven-valent pneumococcal conjugate vaccine (PCV7, Prevnar, Wyeth), through 2006. Unfortunately, the database does not allow for identification of causative agents.

Following the introduction of PCV7 in 2000, the portion of young children receiving PCV7 quickly reached very high levels, which resulted in the virtual eradication of invasive pneumococcal disease (IPD) due to the serotypes in the vaccine in children younger than aged 5 years and a significant decrease in the circulation of the those serotypes in the pediatric and adult populations. Pneumococcal serotype replacement has resulted in a small increase in IPD, but the overall rate remains significantly lower than prior to licensing of PCV7.

Since the pneumococcal serotypes in the vaccine are no longer circulating, waning protection against these serotypes with a shift of disease to older children cannot be responsible for the noted increase in pneumonia and empyema. However, recent publications have documented an increase in the frequency of empyema amongst children admitted with pneumococcal pneumonia caused by individual pneumococcal replacement serotypes. Therefore, it is possible that some replacement serotypes are more likely to cause a necrotizing pneumonia with empyema, especially in younger children. Antibiotic resistance is common in replacement serotypes, particularly type 19A, which is now the most common serotype responsible for IPD, which could also contribute to a worse outcome in children with pneumonia.

Another likely explanation for the study findings is the recent emergence of more invasive strains of methicillin-susceptible and methicillin-resistant Staphylococcus aureus. These strains carry one or more virulence factors which appear to increase the risk for necrotizing pneumonia and empyema. An increase in cases of pneumonia with empyema due to S. aureus has been noted in multiple pediatric centers during this time period. Severe secondary S. aureus pulmonary infection is being recognized more frequently following influenza in older children. Pneumococcus and Streptococcus pyogenes also cause secondary pneumonia with empyema following influenza.

Additional data, with outcomes tied to etiologic agents are needed. In the meantime, physicians caring for children should be aware of the increased potential for complicated bacterial pneumonia in previously healthy children, consider empyema in children not responding as expected to initial antibiotic therapy, and choose therapy appropriate for coverage of resistant strains of pneumococcus and S. aureus when empyema is suspected.

– Joseph A. Bocchini, MD

Infectious Diseases in Children Editorial Board member

Disclosure: Dr. Bocchini reports no relevant financial disclosures.

Follow the PediatricSuperSite.com on Twitter.