H1N1 vaccine safe for those with asthma, study shows

Vaccine induces strong immune response in people with asthma

A single dose of inactivated 2009 H1N1 influenza vaccine in people with asthma is safe, according to results from a national clinical trial with a site at Washington University School of Medicine in St. Louis.

The findings, which appear online in the Journal of Allergy and Clinical Immunology, also suggest that individuals over age 60 who have severe asthma may require a larger dose of vaccine.

“This study demonstrates that the use of H1N1 flu vaccine is safe for all patients with asthma,” says Mario Castro, MD, professor of medicine and of pediatrics and principal investigator at the Washington University site. “Patients with asthma who are concerned about the flu vaccine should be reassured. Furthermore, elderly patients with severe asthma should talk to their doctor about receiving high dose flu vaccine.”


People with asthma are at risk for developing severe disease when infected with the influenza virus. In addition, there is concern that the long-term use of corticosteroids, which are used to control asthma symptoms and known to suppress the immune system, by people with severe asthma might affect their ability to mount a healthy immune response to the vaccine.

“Asthma was the most common underlying health condition among those hospitalized in the United States with 2009 H1N1 influenza infection during the 2009-2010 influenza season,” says Anthony S. Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, a study cosponsor. “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. This is important because the H1N1 vaccine is one component of the seasonal influenza vaccine currently being distributed for the 2010-2011 influenza season.”

“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,” says Susan B. Shurin, MD, acting director of the National Heart, Lung, and Blood Institute (NHLBI), another study cosponsor.

In late 2009, the National Institutes of Health (NIH) rapidly designed and sponsored a clinical study to determine the dose and number of doses of the 2009 H1N1 influenza vaccine needed to safely produce a protective immune response in people with asthma. NIH worked with the Department of Health and Human Services Biomedical Advanced Research and Development Authority to acquire H1N1 vaccine for the study from a U.S.-licensed influenza vaccine manufacturer. The trial was conducted at NHLBI Severe Asthma Research Program (SARP) sites located at university hospitals and centers throughout the United States, including Washington University.

The study enrolled 390 people aged 12 to 79 with asthma. About 70 patients participated at the Washington University site. Participants were divided into two groups. The first group exhibited mild or moderate asthma, and the second group exhibited severe asthma.

For the study, people with mild or moderate asthma were characterized as needing no or low to moderate doses of inhaled corticosteroids to control their disease symptoms. Those with severe asthma needed high doses of inhaled corticosteroids and frequently required oral corticosteroids to control their symptoms.

Half of the participants in each group received a 15-microgram dose of vaccine, and the other half received a 30-microgram dose, both by injection. Three weeks later, each participant received a second dose in the same amount as the first dose. The vaccine, manufactured by Novartis, contained inactivated 2009 H1N1 influenza virus.

The investigators measured the level of antibodies against the 2009 H1N1 influenza virus in participants’ blood samples, which were taken three weeks after each injection, to assess the strength of the immune response.

The vaccine proved safe and effectively produced an immune response that indicated protection against the virus. In participants with mild to moderate asthma, and in most participants with severe asthma, a single 15-microgram dose was sufficient to induce a presumably protective immune response. The immune response was not further improved after a second dose, indicating that a single dose was adequate.

Participants older than age 60 with severe asthma had diminished immune responses to the 15-microgram dose of vaccine, but the 30-microgram dose gave an adequate response.

Participants were followed for any side effects they may have experienced from the vaccine, as well as for asthma attacks that occurred during the study. The vaccine did not exacerbate participants’ asthma. In addition, the vaccine was well tolerated, and its safety profile was found to be the same as that obtained in other studies in which the vaccine was given to the general public.

Washington University School of Medicine’s 2,100 employed and volunteer faculty physicians also are the medical staff of Barnes-Jewish and St. Louis Children’s hospitals. The School of Medicine is one of the leading medical research, teaching and patient care institutions in the nation, currently ranked fourth in the nation by U.S. News & World Report. Through its affiliations with Barnes-Jewish and St. Louis Children’s hospitals, the School of Medicine is linked to BJC HealthCare.