The flu season has passed, but here's some important news for parents to arm themselves with before next fall.

A new study published in Pediatrics on June 4 said a flu shot is key for children with asthma to keep them out of the emergency room.

Researchers at the University of Montreal found that asthma treatments are more likely to fail in children who have the flu.

"We now know that if these kids get the flu, the risks are very high that emergency treatment for an asthma attack will fail," said study co-author Francine Ducharme, a pediatrician and clinical epidemiologist. "Instead of having an overall 17-percent risk of treatment failure, with flu their risk rises to almost 40 percent."

Asthma is a chronic disease of the airways, and about 1 in 12 U.S. children have asthma, according to the Asthma and Allergy Foundation of America.

Flu shots worth it, especially for preschoolers

Ducharme and her colleagues warned that preschoolers are particularly vulnerable.

"These kids should get their flu shot and they should get it systematically — it's worth it," Ducharme said in a university news release.

The study examined 1,000 children treated for moderate to severe asthma attacks in five Canadian emergency rooms. They also analyzed nose swabs taken from kids to determine if they had to flu or another respiratory virus.

About two-thirds tested positive for a viral infection. But when given the standard treatments for an asthma attack, which included oral corticosteroids and inhaled bronchodilators, 19 failed to respond to their medications.

Asthma meds fail with flu

Those with influenza or parainfluenza had a 37 percent higher chance of not responding to asthma treatment, compared to 13 percent for children without the virus.

Asthma treatment was also more likely to fail among children with respiratory syncytial virus (RSV), according to the study. But a bit of good news — the common cold did not reduce the effectiveness of asthma treatment.

Easy way to get protection

The study authors say that the flu shot is well-known for being fallible but it does offer some simple protection for people with asthma againt flu-related complications.

"Influenza is the only respiratory virus that is vaccine-preventable. Granted, it's at best only 50 percent efficacious, but that's no reason for kids with asthma not to get vaccinated yearly, in the fall, before flu season starts," said co-author Caroline Quach, an associate professor of microbiology and infectious diseases at the University of Montreal.