Influenza-associated pneumonia linked to poorer outcomes for hospitalized children

**Dawood FS. Pediatr Infect Dis J. 2010; 29:585-590.**

Hospitalized children with influenza-associated pneumonia had higher rates of intensive care unit admission, respiratory failure and death compared with hospitalized children with influenza who did not have the disease, according to recent study data.

Using the Emerging Infections Program Network, researchers from several institutions gathered information on children aged younger than 18 years with laboratory-confirmed influenza from 2003 to 2008. Inclusion criteria also dictated that the children must have had a chest radiograph during hospitalization. Data came from various states and regions in the United States, with the number of sites growing per influenza season.

The researchers collected information on pre-existing conditions, comorbidities and influenza vaccination status through medical records and, in the case of immunization, state registries if available.

Of the 4,015 children with laboratory-confirmed influenza identified during the study period, 2,992 had a chest radiograph. Of these, 36% had influenza-associated pneumonia, according to the researchers.

When compared with children who did not have the disease, median time before symptom onset and hospitalization was longer for children with influenza-associated pneumonia (3 days vs. 2 days, P<.01). Median length of hospitalization was also longer for this group (4 days vs. 3 days, P<.01).

Children with influenza-associated pneumonia also had higher rates of ICU admission compared with those who did not have the disease (21% vs. 11%, P<.01), according to the researchers. Respiratory failure requiring mechanical ventilation was also more common among this population (11% vs. 3%, P<.01).

Overall, 0.9% of children with influenza-associated pneumonia and 0.3% of those without the disease died during the study (P=.01).

Data revealed that risk for any type of pneumonia was higher among children aged 6 to 23 months (OR=1.9; 95% CI, 1.6-2.3) and those aged 2 to 4 years (OR=1.7; 95% CI, 1.4-2.2) when compared with children aged 5 to 17 years.

Children with the following conditions were also at an increased risk for pneumonia than those hospitalized just for influenza:

Asthma (OR=1.5; 95% CI, 1.1-1.6).
Cardiovascular disease (OR=1.7; 95% CI, 1.1-2.5).
Developmental delay (OR=1.5; 95% CI, 1.1-2.1).
Neuromuscular disorders (OR=1.7; 95% CI, 1.1-2.5).

Children with hemoglobinopathies or immunosuppressive conditions, however were less likely to develop pneumonia.

Results indicated that boys were more likely to have influenza-associated pneumonia, and 54% of cases occurred in children aged younger than 2 years. Asthma appeared as the most prevalent pre-existing condition and affected 24% of the study population with influenza-associated pneumonia.

Twenty-one percent of children with influenza-associated pneumonia initiated antiviral treatment during their hospital stays, yet they were no more likely than children with influenza who did not have pneumonia to receive antiviral medications.

The researchers noted that 886 children aged at least 6 months were eligible for vaccination but only 39% received one dose or more of the vaccine. However, immunization status was missing for 13% of children in this age range.

Data also demonstrated that 2% of children with influenza-associated pneumonia had invasive bacterial coinfection, according to the researchers, with Staphylococcus aureus appearing as the most common pathogen.

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