Researchers at the University of Wisconsin School of Medicine and Public Health have begun administering a national clinical trial aimed at determining the proper swine flu vaccine dosage to immunize asthmatic patients against the H1N1 virus.

Evidence suggests the H1N1 vaccination dosage that is administered to the general population does not provide full protection for asthmatics, according to Lisa Brunette, spokesperson for UW Hospital and Clinics. The trial will determine what dosage provides asthmatics with complete immunization.

According to Sarah Van Orman, executive director of University Health Services, many asthmatics take a type of steroid to control their asthma that serves as a “damper on the immune system.”

According to a statement released by UW Hospital and Clinics, a 2004 study suggested some steroids used to treat asthma might inhibit the effectiveness of regular dosages of flu vaccines.

UW is one of seven research institutions across the country that will participate in the National Institutes of Health asthma trial to evaluate the safety and efficacy of the vaccine in asthma patients.

According to William Busse, UW medical professor and principal investigator of the study, patients with asthma have underlying health conditions that make them more susceptible to infections that are more prevalent among asthmatics, suggesting they may require a different vaccination strategy.

Asthmatics are four times more likely to be hospitalized due to H1N1 complications, and 25 to 30 percent of all patients hospitalized with H1N1 have asthma, Busse said.

“We don’t know exactly why patients with asthma are having so much difficulty with H1N1, but there are a number of situations that raise concern that this is an at-risk group,” Busse said.

Asthmatics are particularly at risk for severe viral pneumonia as a result of influenza and are also more likely to suffer from bacterial infections days after becoming infected with influenza viruses, according to Van Orman.

Busse said H1N1 does not exacerbate asthma symptoms but makes complications more likely in people with asthma.

“It’s not necessarily worsening their asthma, but it’s making them susceptible to the pneumonias and other complications of the influenza,” Busse said.

The study’s 350 participants will be divided into two groups depending on the severity of their asthma. Researchers will administer two 15-microgram doses to half of the participants in each group, and the other half will receive two 30-microgram doses over the course of the 42-day trial, according to Busse. They will not be administering a placebo in this study.

“I think what it can tell us is we may need to do some modifications in the future as far as vaccination,” Busse said. “These are individuals that may either need a larger dose or they may need some other levels of protection.”

Van Orman said asthmatics should get the H1N1 vaccination, which is currently available at UHS for health care workers and people at risk for influenza complications.