Full influenza vaccination greatly reduced ICU admission in children

Issue: April 2014

Immunization with seasonal influenza vaccine reduced by 74% children’s risk for influenza-related intensive care hospitalization, according to recent study results published in the Journal of Infectious Diseases.

“These study results underscore the importance of an annual flu vaccination, which can keep your child from ending up in the intensive care unit,” Alicia Fry, MD, a medical officer in the CDC’s Influenza Division, said in a press release. “It is extremely important that all children — especially children at high risk of flu complications — are protected from what can be a life-threatening illness.”

Jill M. Ferdinands, PhD, of the CDC’s influenza division, and colleagues evaluated children aged 6 months to 17 years during the 2010-2011 and 2011-2012 influenza seasons to determine the effectiveness of influenza vaccine against ICU admission. Children in the study were admitted to 21 pediatric ICUs and identified as patients with acute severe respiratory illness of less than 7 days’ duration and who tested positive for influenza by real-time reverse-transcription PCR (n=44); patients who tested negative were controls (n=172). Community controls in the study consisted of a matched sample of children who resided in the same geographic area but were not hospitalized with influenza between September of the study year and the matched case’s pediatric ICU admission date (n=93).

At least one underlying chronic medical condition was found in 55% of cases and 69% of pediatric ICU controls. Moderate or severe respiratory conditions (P=.02) and disorders involving an aspiration risk (P=.04) were more common among pediatric ICU controls than cases; however, pediatric ICU controls were less likely to have chronic cardiac conditions compared with cases (P=.03).

Overall, 29% of cases and pediatric ICU controls were fully vaccinated compared with 51% of community controls. Following up on parental reports of full vaccination, 27% of cases and 32% of pediatric ICU controls did not have evidence of full vaccination.

Sixty-one percent of pediatric ICU controls had a non-influenza pathogen identified. Respiratory syncytial virus was confirmed among 76 patients admitted to pediatric ICUs.

Influenza A was isolated from 72% of patients, and influenza B from 28% of patients. Full influenza vaccination effectiveness was 74% using the comparison of cases to pediatric ICU controls. Partial vaccination did not show any benefit.

“Because some people who get vaccinated may still get sick, it’s important to remember to use our second line of defense against flu: antiviral drugs to treat flu illness,” Fry said. “People at high risk of complications should seek treatment if they get a flu-like illness. Their doctors may prescribe antiviral drugs if it looks like they have influenza.”

In an accompanying editorial, Timothy R. Peters. MD, and Katherine A. Poehling, MD, MPH, both of the department of pediatrics at Wake Forest School of Medicine in Winston-Salem, N.C., said the findings “demonstrate that influenza vaccination prevents severe disease in children, and reminds us of the importance of vaccination for children with risk factors for severe influenza.”

For more information:

Ferdinands JM. J Infect Dis. 2014;doi:10.1093/infdis/jiu185.

Peters TR. J Infect Dis. 2014;doi:10.1093/infdis/jiu187.

Disclosure: The study was funded in part by the CDC. The researchers report no relevant financial disclosures.