Children Vaccinated for Flu at Three Times the Risk for Hospitalization than Unvaccinated Peers

...and those with asthma at a higher risk of hospitalization if they get the flu vaccine.

The American Thoracic Society: Flu Shot Not Effective in Preventing Flu-Related Hospitalizations in Asthmatic Children
News Release
FOR RELEASE MAY 19, 2009 at 1:30 p.m. PDT

FOR MORE INFORMATION, CONTACT:
Keely Savoie or Brian Kell
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Flu Shot Not Effective in Preventing Flu-Related Hospitalizations in Asthmatic Children

ATS 2009, SAN DIEGO— The inactivated flu vaccine does not appear to be effective in preventing influenza-related hospitalizations in children, especially the ones with asthma. In fact, children who get the flu vaccine are more at risk for hospitalization than their peers who do not get the vaccine, according to new research that will be presented on Tuesday, May 19, at the 105th International Conference of the American Thoracic Society in San Diego.

Flu vaccine (trivalent inactivated flu vaccine—TIV) has unknown effects on asthmatics.

“The concerns that vaccination maybe associated with asthma exacerbations have been disproved with multiple studies in the past, but the vaccine’s effectiveness has not been well-established,” said Avni Joshi, M.D., of the Mayo Clinic in Rochester, MN. “This study was aimed at evaluating the effectiveness of the TIV in children overall, as well as the children with asthma, to prevent influenza-related hospitalization.”

The CDC’s Advisory Committee on Immunization Practices (ACIP) and the American Academy of Pediatrics (AAP) recommend annual influenza vaccination for all children aged six months to 18 years. The National Asthma Education and Prevention Program (3rd revision) also recommends annual flu vaccination of asthmatic children older than six months.

In order to determine whether the vaccine was effective in reducing the number of
hospitalizations that all children, and especially the ones with asthma, faced over eight consecutive flu seasons, the researchers conducted a cohort study of 263 children who were evaluated at the Mayo Clinic in Minnesota from six months to 18 years of age, each of whom had had laboratory-confirmed influenza between 1996 to 2006. The investigators determined who had and had not received the flu vaccine, their asthma status and who did and did not require hospitalization. Records were reviewed for each subject with influenza-related illness for flu vaccination preceding the illness and hospitalization during that illness.

They found that children who had received the flu vaccine had three times the risk of hospitalization, as compared to children who had not received the vaccine. In asthmatic children, there was a significantly higher risk of hospitalization in subjects who received the TIV, as compared to those who did not (p= 0.006). But no other measured factors—such as insurance plans or severity of asthma—appeared to affect risk of hospitalization.

“While these findings do raise questions about the efficacy of the vaccine, they do not in fact implicate it as a cause of hospitalizations,” said Dr. Joshi. “More studies are needed to assess not only the immunogenicity, but also the efficacy of different influenza vaccines in asthmatic subjects.”

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Session # C94: “Viral Infections in Childhood Respiratory Disease”
Abstract # 561: “Flu Vaccination in Asthmatics: Does It Work?”
http://www.call4abstracts.com/ats/society_admin/abs_preview.php?absnum=561
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ATS 2009 · San Diego
International Conference
Abstract Number: 561
Contact/Presenting Author: Avni Y. Joshi
Department/Institution: Internal Medicine, Mayo Clinic
Address: 200, First St. SW
City/State/Zip/Country: Rochester, MN, 55905
Phone: 01-507-284-2511 Fax: 01-507-284-0902 E-mail: joshi.avni@mayo.edu
ATS member: No Student or in training: Yes
Funding Source: None.
Abstract Category: 14.03 - Pediatric Asthma
Presentation format: Either Poster or Oral
Preview Disclosure
Travel Award: Yes
Publication of email address: Yes, joshi.avni@mayo.edu
I confirm that all authors listed on this abstract have knowledge of the abstract submission:
Yes
Title: Flu Vaccination in Asthmatics: Does It Work?
A. Y. Joshi, MD1, V. N. Iyer, MD,MPH1, M. F. Hartz, MD1, G. W. Volcheck, MD,Ph.D1, A. M. Patel,
MD1 and J. T. Li, MD,Ph.D1. 1Mayo Clinic College of Medicine, Rochester, MN.
INTRODUCTION: Influenza is known to be associated with asthma exacerbation but the
effectiveness of the trivalent inactivated flu vaccine (TIV) in asthmatics is unknown.

METHODS: We conducted a cohort study of all pediatric subjects( 6 months to 18 years age) who were evaluated at Mayo Clinic, Rochester, MN, USA who had laboratory confirmed influenza during each flu season from 1999-2006 to evaluate the efficacy of TIV. A case control analysis was performed with the cases and the controls being the subjects with asthma who did and did not required hospitalization with the influenza illness respectively.

RESULTS:
There were 236 subjects with laboratory confirmed influenza from 1996-2006.

In assessing the effectiveness of the TIV for preventing hospitalization with influenza in all subjects, there was an overall trend towards higher rates of hospitalization in subjects who got the TIV as compared to the ones who did not get the TIV( OR:2.97, CI: 1.3,6.7).Using Cochran-Mantel-Haenszel (CMH) test for Asthma status stratification, there was a significant association between hospitalization in asthmatic subjects and TIV (P=0.006).

http://www.call4abstracts.com/ats/society_admin/abs_preview.php?absnum=561 (1 of 2) [5/11/2009 1:43:56 PM]
http://www.call4abstracts.com/ats/society_admin/abs_preview.php?absnum=561
In the asthmatic subset:
There was no association between ER visit and receiving the TIV ,severity of asthma and the risk of hospitalization or the hospital length of stay and receiving the TIV.

In assessing access to medical care, there was no association between hospitalizations and health care insurance plans (Odds ratio:0.3, P= 0.13)

CONCLUSION:
1) TIV did not provide any protection against hospitalization in pediatric subjects' esp. children with asthma. On the contrary, we found a 3- fold increased risk of hospitalization in subjects who did get the TIV vaccine.This may be a reflection not only of the vaccine effectiveness but also the population of children who are more likely to get the vaccine.

2) More studies are needed to assess not only the immunogenicity but also efficacy of different influenza vaccines in asthmatic subjects.
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