No change in pneumonia rates with Prevnar vaccines

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" 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.

"

http://www.pediatricsupersite.com/view.aspx?rid=81072

Posted on the Pediatric SuperSite on March 1, 2011

Outpatient CAP rates remain stable, despite vaccination

Kronman MP.

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

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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.

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.

– ph A. Bocchini, MD

Infectious Diseases in Children Editorial Board member

Disclosure: Dr. Bocchini reports no relevant financial

disclosures.

Sheri Nakken, former R.N., MA, Hahnemannian

Homeopath

Vaccination Information & Choice Network, Washington State, USA

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