Children who are born prematurely have more than four times the risk of severe flu complications, despite not being considered a high-risk group by U.S., U.K., or World Health Organization guidelines, according to findings from a meta-analysis.
In keeping with existing guidelines, the systematic review and meta-analysis of 27 studies involving 14,086 children also identified children with neurologic disorders (odds ratio, 4.62; 95% confidence interval, 2.82-7.55), sickle cell disease (OR, 3.46; 95% CI, 1.63-7.37), immunosuppression (OR, 2.39; 95% CI, 1.24-4.61), and diabetes (OR, 2.34; 95% CI, 1.20-4.58) at increased risk of flu complications.
The presence of multiple medical conditions significantly increased the risk of hospital admission from 52% (one condition) to 74% (>1 condition), according to Peter J. Gill, D.Phil., of the University of Oxford (England), and associates (Lancet Respir. Med. 2014 Dec. 4 [doi:10.1016/S2213-2600(14)70252-8]).
There was no significant association between hospital admission for influenza and asthma or other respiratory conditions, obesity, heart conditions, or cancer, according to the investigators.
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Five of the seven studies in the analysis did not define prematurity by gestational age.
In a linked comment, however, Dr. Harish Nair of the University of Edinburgh (Scotland) and Dr. Marc-Alain Widdowson of the U.S. Centers for Disease Control and Prevention, Atlanta, said that this particular finding should be interpreted with caution, as the authors measured the risk of hospitalization among children already seeking care.
“If respiratory disease or asthma is already associated with seeking ambulatory care for influenza, then these characteristics might not have been identified as risk factors,” they wrote (Lancet Respir. Med 2014 Dec. 4 (doi:10.1016/S2213-2600(14)70285-1).
They also advised caution on the prematurity finding, as five of the seven studies in the analysis did not define prematurity by gestational age. If confirmed, however, it could have “major policy implications” as 11% (15 million) of the world’s babies are born preterm.
“Current WHO guidelines for seasonal influenza vaccination do not include preterm babies in the list of high-risk groups, but perhaps the new findings support their eventual inclusion,” Dr. Nair and Dr. Widdowson wrote.
Protection of these susceptible children, however, comes with challenges. “Children cannot be vaccinated before age 6 months; inactivated vaccines are poorly immunogenic in young children, necessitating two doses, and live, attenuated influenza vaccines are only recommended in children aged 2 years or older,” they noted.