Dec 13, 2010 (CIDRAP News) – A standard dose of H1N1 influenza vaccine appears to work well in people who have asthma, but older patients with severe asthma may need a higher dose, a government-sponsored trial has shown.
Those with asthma are at risk for serious complications when they contract flu, and asthma was the most common preexisting health problem in flu patients who were hospitalized during the 2009 H1N1 pandemic, the National Institutes of Health (NIH) said in a press release about the study today.
In addition, there is concern that asthma patients might not mount a strong immune response to the vaccine because they are often treated with corticosteroids, which suppress the immune system, the agency said.
"The results of this clinical trial show that the 2009 H1N1 influenza vaccine was safe and led to adequate production of antibodies thought to be protective against the virus," Anthony S. Fauci, MD, director of the NIH's National Institute of Allergy and Infectious Diseases (NIAID), said in the release. The H1N1 vaccine is included in this year's seasonal flu vaccine.
However, asthma patients older than 60 needed a 30-microgram (mcg) dose of vaccine, double the standard 15-mcg dose, to generate an adequate immune response, the agency said. The study was published online by the Journal of Allergy and Clinical Immunology.
In the study, conducted late in 2009, researchers from the NIH and a number of institutions around the country enrolled 390 asthma patients from 12 to 79 years old. They were divided into two groups, one with mild or moderate asthma and the other with severe asthma. Those with severe asthma needed high doses of inhaled corticosteroids and, often, oral corticosteroids to control their symptoms.
By random assignment, half of the participants in each group received a 15-mcg dose of vaccine and half received 30 mcg, and 3 weeks later they received a second dose. A satisfactory immune response (seroprotection) was defined as a hemagglutination inhibition assay titer of 1:40 or greater.
In the 217 patients with mild-to-moderate asthma, one 15-mcg dose induced seroprotection in 90.6%, and a 30-mcg dose induced seroprotection in 95.3%, according to the study abstract. Among the 173 patients with severe asthma, a 15-mcg dose was seroprotective for 77.9%, and 30 mcg proved seroprotective in 94.1%. The second dose did not increase the level of seroprotection for either group.
Volunteers who were over 60 and had severe asthma had the lowest rate of seroprotection, at 44.4% with 15 mcg of vaccine, but the 30-mcg dose yielded a seroprotection rate of 88.9% in that group, according to the study.
"We were not surprised that the older participants had less robust responses to the vaccine compared with the younger participants because immune system activity tends to decrease with age," said William Busse, MD, an asthma investigator in the NIH's National Heart, Lung and Blood Institute (NHLBI) and professor of medicine at the University of Wisconsin in Madison, in the NIH release.
"Based on these observations, physicians may wish to consider immunizing older patients who have severe asthma with the high-dose version of the 2010-2011 seasonal influenza vaccine, which contains the 2009 H1N1 influenza virus component," said Busse, lead author of the study.
The high-dose vaccine, sold by Sanofi Pasteur as Fluzone High-Dose, was approved by the Food and Drug Administration in December 2009. It contains 60 mcg of each of three flu strains included in the standard seasonal vaccine, four times the normal amount.
The acting director of the NHLBI, Susan B. Shurin, MD, said in the release, "This study shows patients and their doctors that it is safe and effective to get the flu vaccination while they continue to take the corticosteroid medications necessary to keep their asthma under control."
The vaccine was well-tolerated and did not exacerbate patients' asthma, the NIH said. Its safety profile was found to be the same as seen in studies in which the vaccine was given to the general public.
Busse WW, Peters SP, Fenton MJ, et al. Vaccination of patients with mild and severe asthma with a 2009 pandemic H1N1 influenza virus vaccine. J Allergy Clin Immun 2010; early online publication [Abstract]
Dec 13 NIH press release