ATS 2009: Flu Vaccination May Triple Risk for Flu-Related Hospitalization in Children With Asthma

Trivalent inactivated flu vaccine (TIV) was not an effective protection against hospitalization in pediatric populations, particularly in children with asthma; in fact, there was a 3-fold increased risk for hospitalization in asthmatic children who received the TIV, according to a study released here at ATS 2009: the American Thoracic Society International Conference. However, experts agree that this is not a reason to stop vaccinating children with asthma, because the vaccine is still helpful in making protective antibodies.

Dr. Avni Joshi

"The flu shot is a killed vaccine. Inherently, it's a safe vaccine so we tend to give it to everyone, but we don't think about how effective it is — especially in asthmatic children," lead investigator Avni Joshi, MD, fellow, instructor in pediatric medicine, and fellow-in-training in allergy and infectious diseases, Division of Allergic Diseases, Mayo Clinic, Rochester, Minnesota, told Medscape Pulmonary Medicine in an interview after her presentation. "Just because a flu shot has proved to be very safe for kids, especially those with asthma, [doesn't mean we] know how effective it is in preventing hospitalizations in cases of influenza in all children, particularly those with asthma."

Currently, the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices and the American Academy of Pediatrics recommend annual influenza vaccination for all children 6 months to 18 years. The National Asthma Education and Prevention Program (third revision) also recommends annual flu vaccination of asthmatic children older than 6 months.

This was a cohort study that evaluated the efficacy of TIV in all pediatric patients 6 months to 18 years with laboratory-confirmed influenza (263 children) who were seen at the Mayo Clinic during flu seasons from 1999 to 2006. TIV has unknown effects on patients with asthma.

Dr. Joshi and colleagues determined which subjects had received the flu vaccine and which subjects had not. They then looked at asthma status, and determined which subjects required hospitalization and which did not. The record for each subject in which flu vaccination status was noted before illness and hospitalization was reviewed.

The study found an overall trend toward higher rates of hospitalization in subjects who received TIV than in those who did not (odds ratio [OR], 2.97; 95% confidence interval [CI], 1.3 - 6.7). They used the Cochran-Mantel-Haenszel test for asthma-status stratification, and documented a significant association between hospitalization in the asthmatic subjects and TIV (P = .006). The severity of asthma did not determine the risk for hospitalization or length of hospital stay. There was also no association between emergency-department visits and having received TIV. In looking at access to medical care, no association between hospitalizations and healthcare insurance plans was found (OR, 0.3; P = .13).

Dr. Joshi pointed to studies that have looked at whether FluMist (a live intranasal influenza virus vaccine) is more effective when there is a mismatch between the vaccine strain and the circulating strain. "But the safety of live vaccine has been questioned by various studies," she said. "It appears to trigger wheezing episodes, especially in children under 2. This study opens the doors to looking at live vaccines, to which we say no most of the time, especially in asthmatics."

Dr. Joshi emphasized: "We should continue vaccinating all children, but continue our quest to find a more effective influenza vaccine."

Dr. Anthony M. Szema

Anthony M. Szema, MD, assistant professor of medicine and surgery at SUNY Stony Brook School of Medicine in New York, commented on Dr. Joshi's study: "These authors do not address mortality protection or specific [immunoglobulin G] antibody production. Nevertheless, the take-home message is that parents should continue to vaccinate their healthy and asthmatic children, but should not be lulled into a false sense of security that, should their children succumb to the flu, this vaccination will prevent hospitalization."

"The point is, if they have asthma and are unlucky enough to get the flu, they're going to get hospitalized more often if they have asthma; this is not a reason to say, 'I'm not going to vaccinate my kids.' Vaccines are supposed to protect against morbidity and mortality against the flu," said Dr. Szema, who said he agreed with Dr. Joshi that a next-generation vaccine that would be able to protect against hospitalization in the asthmatic population would be ideal. "What we have now is helpful in making protective antibodies, but is not completely protective, especially in asthmatics who already have inflamed airways."

ATS 2009: American Thoracic Society International Conference: Abstract 561. Presented May 19, 2009.

Source : http://www.medscape.com/viewarticle/703235?sssdmh=dm1.476505&src=nldne