ST. LOUIS—A clinical trial sponsored by the American Lung Association (ALA) should alleviate concern that influenza vaccination may increase susceptibility to asthma exacerbations.[1] In the study, “vaccination was safe for patients with asthma, regardless of asthma severity,” principal investigator Mario Castro, MD, MPH, told RESPIRATORY REVIEWS. Furthermore, vaccination was found to be safe for both adults and children.

In the study, the rate of asthma exacerbations during the two weeks after administration of either the flu vaccine or placebo was quite similar—28.8% vs 27.7%, respectively. Nor were any differences in exacerbation rates found during subgroup analyses. In addition, there were no differences in the frequency of other asthma-related outcomes between the vaccine and placebo cohorts, added Dr. Castro, an Assistant Professor of Pulmonary and Critical Care Medicine at the Washington University School of Medicine in St. Louis.

The 2,032 patients in the trial, all of whom were between the ages of 3 and 64 years, had physician-diagnosed asthma. Most had mild to moderate disease, and all were clinically stable. In double-blind, crossover fashion, the patients received either the inactivated trivalent split-virus influenza vaccine or placebo and then the other injection approximately four weeks later. Order of injections was random. An asthma exacerbation within 14 days of an injection was the primary outcome measure.

The rate of exacerbations within the first three days after injection was similar in the two groups (12.7% vs 13.8%, respectively), and no differences emerged during the two-week follow-up. Subgroup analyses stratified patients by a number of variables, including demographics, smoking status, lung function, and asthma symptoms before enrollment; in none of the subgroups was a difference in exacerbation rate found. Also, no differences following vaccination or placebo administration were detected for five secondary asthma-related outcomes:

• Number of symptom-free days.
• Daily symptom score.
• Percentage of patients with at least a 20% decline in peak expiratory flow from personal best.
• Rate of new or increased medication use for long-term asthma control.
• Percentage of patients who missed at least a day of school or work.

Among the symptoms that patients attributed to the injections, only body aches were more common in the vaccination group than in the placebo cohort.

RESULTS SUPPORT RECOMMENDATIONS

One of the study’s most important findings was that among the patients with more severe asthma, the likelihood of exacerbations following vaccination or placebo injection was similar. This demonstrates, said Dr. Castro, that the flu vaccine is safe even in this higher-risk group.

“The trial reinforces recommendations for annual influenza vaccination in all patients with asthma,” concluded Dr. Castro. The ALA is developing a public education campaign to spread that message.

—Timothy Begany