December 13, 2010
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Each year, the Centers for Disease Control and Prevention (CDC) recommends that people with asthma receive the seasonal influenza vaccine to prevent getting the flu, which may seriously worsen their asthma and thereby increase their risk of severe influenza disease.
People with asthma also were at higher risk of complications following infection with 2009 H1N1 influenza virus. Review of hospital records from February 2009 to April 2010 by CDC from the disease outbreak in the United States found that although asthma occurs in about 8 percent of the U.S. population, approximately 30 percent of people hospitalized due to 2009 H1N1 influenza had asthma.
In the fall of 2009, U.S. public health officials, following the recommendation of the CDC’s Advisory Committee on Immunization Practices, designated people with underlying medical conditions, including asthma, among the top priority groups to receive the 2009 H1N1 influenza vaccine.
This clinical trial of 2009 H1N1 influenza vaccine in people with asthma provided information to public health officials to help answer questions including what dosage and how many doses of vaccine are needed to elicit immune responses indicative of protection against the 2009 H1N1 virus.
People with severe asthma receive high doses of corticosteroids by inhalation and some of them even receive corticosteroids orally or by injections. Sometimes, corticosteroids can suppress the immune system. Therefore, it was important to examine whether the immune response to the H1N1 influenza vaccine was adequate in people with asthma receiving high doses of corticosteroids.
The study enrolled 390 adolescents and adults aged 12 to 79 years with mild, moderate or severe asthma. Participants were categorized by asthma severity into two groups (mild/moderate and severe); by age into four groups (12 to 21 years old, 21 to 39 years old, 40 to 59 years old, and older than 60). A total of 217 people with mild/moderate asthma and a total of 173 people with severe asthma were enrolled in the trial. They were randomly divided within each asthma category to receive a low or high dosage of the inactivated 2009 H1N1 influenza vaccine. The trial was open-label, meaning that the clinicians and participants knew the dosage of vaccine administered.
All participants received two injections of the vaccine spaced three weeks apart. A total of 110 individuals with mild or moderate asthma and 87 individuals with severe asthma received 15-microgram doses of the vaccine. A total of 107 individuals with mild or moderate asthma and 86 individuals with severe asthma received 30-microgram doses of the vaccine. The 30-microgram dose of the vaccine was administered as two 15-microgram injections, one in the muscle of each arm or thigh.
A total of five clinic visits were required during the study period. Vaccine injections were administered on days 1 and 21 of the study. During visits, blood samples were taken and lung function assessed. Every day for one week after each vaccine injection, study participants completed diaries tracking any irritation they observed at the injection site or generalized symptoms they had, which are well-known to occur after vaccinations (e.g., fever, fatigue, etc.).
All participants were provided with a diary on day 1 to track their asthma symptoms and record the number of times they took asthma medications during the study period. Study investigators reviewed diary entries at each of the five clinic visits. Follow-up telephone calls to track participants’ health status were conducted for 6 months after the second dose of the vaccine was given.
The major goal of the study was to determine if people with severe asthma (who were those taking high doses of corticosteroids) require one or two doses of the standard vaccine (15 micrograms) or if they need a higher dose (30 micrograms). Study investigators looked for indications of immune system responses, such as the production of antibodies against 2009 H1N1 influenza virus. Blood samples drawn at set time points following the first and second injections provided information about the immune response to the vaccine. The safety of the vaccine in people with asthma also was assessed.
A detailed description of the study can be found at ClinicalTrials.gov.
The trial enrolled 390 males and non-pregnant females aged 12 to 79 years with mild, moderate or severe asthma.
The study population was drawn from individuals with asthma who had previously participated in a SARP study, as well as from asthma and other clinics in the participating academic institutions.
Participants were extensively characterized with respect to their asthma severity, lung function and airway inflammation. Asthma severity is largely distinguished by the amount and frequency of corticosteroids needed to control asthma symptoms. People with mild disease may not need corticosteroids or may require low doses of inhaled corticosteroids; those with moderate asthma need low to moderate doses of inhaled corticosteroids; and those with severe asthma need high doses of inhaled corticosteroids and frequently use oral corticosteroids.
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Last Updated December 16, 2010
Last Reviewed October 15, 2009