Greater severity of infection in children associated with influenza B than influenza A strain, new study says

By Bianca Jimeno

Although influenza B is often perceived to be milder than influenza A, new research suggests that the severity of infection from influenza B may be greater in children. In a study led by The Hospital for Sick Children (SickKids), data shows that children hospitalized with type B influenza, which infects only humans, had a greater mortality than those infected with type A, the ever-evolving virus that infects both humans and animals and is largely responsible for pandemics.

The study, published in PEDIATRICS drew upon data collected by the Canadian Immunization Monitoring Program ACTive (IMPACT) across 12 paediatric referral hospitals over eight non-pandemic influenza seasons from 2004 to 2013. Of the 4,155 children admitted to IMPACT centres, the proportion of deaths attributable to influenza was significantly greater for children with influenza B at 1.1 per cent, compared to 0.4 per cent for those with influenza A.   

“Traditionally, we think of influenza A as more serious, but we found influenza B to be as severe, if not more severe, in children,” says lead author Dr. Dat Tran, Staff Physician of Infectious Diseases at SickKids. “Fortunately, we now have seasonal flu vaccines that protect against both strains of influenza B, which healthy children of all ages should be immunized against.”

The research also indicated that among healthy children who were hospitalized for influenza B, older children (ages 10 to 16) had the greatest risk of developing severe disease from the infection and were most likely to be admitted to an intensive care unit.