FRIDAY, June 26 (HealthDay News) -- Adults with asthma face a higher risk of complications if they catch the flu, yet many skip their annual shots, new research from the U.S. Centers for Disease Control and Prevention shows.

The lack of vaccinations among those with asthma mirrors inadequate vaccination rates in the general population, said study co-author Dr. Gary Euler, an epidemiologist with the National Center of Immunization and Respiratory Diseases at the CDC. The report appears in the August issue of the American Journal of Preventive Medicine.

Those with asthma did get vaccinated at a higher rate than those who did not have the respiratory condition, but still fell short, the study shows.

It's not known whether swine flu will surge in the coming flu season, complicating the issue even more, Euler noted. "I think we don't know the full extent of what the swine flu is going to be like," he said.

But it is known that typical influenza by itself is associated with a higher rate of complications -- including bacterial infections of the respiratory tract, such as pneumonia -- among those with medical conditions such as asthma.

In the study, Dr. Peng-jun Lu, a senior service fellow at the center, together with Euler and others looked at data from the Behavioral Risk Factor Surveillance System, in place since 1984, which collects information from telephone surveys. The researchers evaluated the responses of more than 173,000 adults, ages 18 to 64, and found that 8.4 percent have asthma.

Among adults 18 to 49 years old who have asthma, 33.9 percent got vaccinated, compared with 54.7 percent of those ages 50 to 64. Among all adults ages 18 to 64 without asthma, the vaccination rate was 28.8 percent.

The findings echo results from a study done in 2008, in which researchers found that too few U.S. teens with asthma and other high-risk illnesses get flu shots. In that study, researchers looked at vaccination rates from 1992 to 2002 for more than 18,000 teens, finding that more than 56 percent did not get flu shots during the four-year period from 1999 to 2002.

Many factors might contribute to the low vaccination rates, said Dr. Clifford Bassett, medical director of Allergy and Asthma Care of New York and a clinical instructor of medicine at New York University School of Medicine.

"Those with asthma may not realize they are in a high-risk group" for flu complications, Bassett said.

Those with asthma might also be overwhelmed because they could already be taking several medications to treat their asthma or don't want to spend more time or money in the doctor's office, he added.

Old-fashioned denial could play a role, too, Bassett noted. The thinking he often hears, he said, is this: "I am OK, I never had the flu, I don't think I need it."

Some with asthma may also mistakenly think a shot would affect their breathing adversely, which is not true, Euler said.

He advises all patients, whether they have asthma or not, to start talking to their doctors about getting vaccinated in the late summer or early fall.

More information

The U.S. Centers for Disease Control and Prevention have more about the flu vaccine.

SOURCES: Clifford Bassett, M.D., medical director, Allergy and Asthma Care of New York, and clinical instructor, medicine, New York University School of Medicine, New York City; Peng-jun Lu, M.D., Ph.D., senior service fellow, and Gary Euler, Dr.P.H., epidemiologist, National Center for Immunization and Respiratory Diseases, U.S. Centers for Disease Control and Prevention, Atlanta; August 2009, American Journal of Preventive Medicine

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