VANCOUVER, B.C. – The risk that a child will be hospitalized with influenza more than doubles if more than half of the household members smoke, maternal age is below 22 years, or household income is below the poverty line.
However, the risk is halved if children are breastfed for 6 months or more, or if caregivers are immunized against the influenza if their children are not, according to Dr. Nila Dharan, who is with New York University's division of infectious diseases.
Dr. Dharan and her colleagues compared the medical and demographic histories of 290 children aged 6-59 months hospitalized with influenza with 1,089 age- and zip code–matched children who were not hospitalized with influenza.
Although most of the risk and protective factors are known, “This study is the largest to date examining the risk of childhood exposure to cigarette smoke and hospitalization for influenza and highlights the importance of reducing children's environmental exposure to smoke, and the need for vaccination of both the child and their household contacts,” she said.
Among other findings, children not current with their vaccinations had a greater risk of influenza hospitalization (odds ratio 1.7), highlighting “the benefits of routine childhood vaccinations which may reduce the risk of secondary bacterial infections,” Dr. Dharan said at the meeting.
Of all the risk factors, however, preexisting medical conditions were the most significant, including pulmonary and neurologic conditions, but especially hematologic or oncologic ones (OR 12.1).
The study found a statistically significant trend toward greater protection the longer children are breastfed. Breastfeeding for their first year or longer was protective for children aged 2-5 years (OR 0.5); not being breastfed increased the risk of influenza-hospitalization (OR 1.7).
Day care did not increase influenza hospitalization risk (OR 1.1), but being a boy did (OR 1.3).
The study culled information during the 2005-2008 influenza seasons from 10 sites in the Center for Disease Control and Prevention's Emerging Infections Program.
Dr. Dharan said that she has no disclosures.