Influenza viruses account for a significant number of health care visits and hospitalizations annually, despite the availability of an effective vaccine. Children with asthma are at higher risk for serious sequelae of influenza; therefore, they should be vaccinated annually. However, the vaccination rate in this group of patients is less than 10 percent. Physicians may be reluctant to vaccinate these children because it is believed that patients taking corticosteroids have an impaired response to the vaccine. Consequently, many physicians will not give the vaccine to children having an acute exacerbation of asthma. Fairchok and colleagues evaluated the immunogenicity of the influenza vaccine in children who were taking high-dose prednisone for asthma.

Children between the ages of six months and 18 years who presented to a military pediatric clinic with moderate to severe asthma were eligible for the study. Children who required administration of glucocorticoids comprised the treatment group; those who did not comprised the control group. Exclusion criteria included known contraindications to the influenza virus vaccine, recent glucocorticoid therapy or the use of more than 900 mg per day of inhaled steroids or long-term oral steroids. Children in the treatment group received a five-day course of prednisone (2 mg per kg per day) within 48 hours of enrollment. All children were immunized with the standard trivalent influenza vaccine, and those younger than nine years who had not previously been vaccinated were given a booster four to six weeks later.

Serum samples were obtained at baseline and three to six weeks after the vaccination to measure the presence of three antibodies to the influenza virus. An immunologic response was defined as a fourfold or greater increase in the antibody titer from baseline. A postvaccination titer of at least 1:40 was considered a protective immune response.

Fifty-eight children were enrolled over a three-month period, and 50 ultimately completed the study. Most of the patients were boys about 9.6 years of age. Neither group experienced severe adverse effects, an increase in symptoms, or the need for increased use of medication after receiving the vaccine. All children responded well to the A/H1N1 and A/H3N2 antigens, but rather poorly to the B antigen. There were no significant differences in serologic responses between groups or in the number of children who had protective antibody titers of at least 1:40. Children in the treatment group had a greater overall immunologic response to all three components of the vaccine, although these numbers were not statistically significant.

The authors conclude that high-dose prednisone therapy does not diminish the effectiveness of the influenza vaccine in children with asthma. Because the vaccine does not exacerbate asthma symptoms and, in fact, provides a protective immunologic response, physicians should administer the vaccine concurrently, when indicated, to children who are undergoing treatment of acute asthma.