December 10, 2004

Study reveals disparities in flu vaccine rates

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Frank Boehm, M.D., holding his 18-month-old grandson Seth Boehm, was all smiles after being honored at the 30th Annual High-Risk Obstetrics Conference. On hand for the event were, from left, Connie Graves, M.D., interim director of Maternal-Fetal Medicine; Steven Gabbe, M.D., dean of VUSM; Stephen Entman, M.D., chair of OB/GYN; and Harry Jacobson, M.D., vice chancellor for Health Affairs.
photo by Dana Johnson

Study reveals disparities in flu vaccine rates

Last year ushered in a swirl of notoriety regarding influenza vaccine. The 2003-2004 flu season arrived early, hit hard and, thanks in part to tremendous media hype and a delay in the availability of vaccine supplies, flu shots were a highly sought-after commodity.

Or so it seemed.

Despite the high visibility of last year's flu season, a new study shows that a significant number of Tennesseans either chose not to receive flu vaccine or may have encountered a barrier to access. Researchers with the Tennessee Department of Health and Vanderbilt University Medical Center's Department of Preventive Medicine conducted a survey of Tennessee citizens finding significant disparities in the rates of influenza vaccination.

With all the media attention and preventive health awareness focused on influenza, investigators wanted to know why individuals would choose not to be vaccinated, or if they wanted to receive flu vaccine, what barriers stood in their way.

In a study just published in the journal Clinical Infectious Diseases, more than 4,000 Tennesseans were surveyed after last year's flu season as to whether they received a flu vaccination. If the respondent was not vaccinated he or she was asked why. The study offers insight into access to care and the public's perceptions of flu vaccine that may allow infectious diseases practitioners to guide future immunization policies.

The study's principal investigator, Timothy F. Jones, M.D., initiated the survey because he believes that understanding the public's perception of influenza vaccination, and variables that influence or impede the public's decision to get immunized, is critical if immunization rates are to be improved.

“Unfortunately, despite recent vigorous efforts to get the word out to educate medical providers and the public, in four of the last five flu seasons there have been unfortunate situations that might have presented barriers to immunization such as delays and shortages of vaccine,” said Jones, deputy state epidemiologist for Communicable and Environmental Disease Services at the Tennessee Department of Health and assistant clinical professor of Preventive Medicine at VUMC.

“With our close relationship between the (State) Department of Health and Vanderbilt we were ideally poised to perform this fairly large survey quickly and efficiently. It is quite remarkable that we managed to complete the entire survey, from conception and analysis to dissemination of the results, in less than a year. This is particularly important given the huge problems with shortages this year. The events of this year are nothing we could have predicted, but I think these data contribute substantially to understanding many of the complex issues that are being raised this winter during this time of flu vaccine shortage.”

Slightly more than one-half of the total number of study respondents indicated they were vaccinated last year either at a private medical clinic, their workplace, a health department or pharmacy.

Three-fourths of survey respondents indicated having a health risk factor for which the Centers for Disease Control and Prevention recommends vaccination. In spite of this, 41 percent of respondents in high-risk categories indicated they chose not to be vaccinated.

The survey also found that more than 40 percent of respondents over age 50, more than half of the surveyed health care workers, and 70 percent of pregnant women surveyed were not immunized for influenza.

“We continue to face two problems: doctors still have not informed all their high-risk patients that they need influenza vaccine, and many patients remain concerned about the myth that they can get flu from the flu vaccine,” said William Schaffner, M.D., professor and chairman of the Department of Preventive Medicine and a co-author of the study.

The survey also found African Americans, rural residents, and the state's lower-income residents were significantly less likely to be vaccinated than others. Six percent of the survey's respondents who eventually received flu vaccine reported difficulty obtaining a shot. Only eight percent of respondents reported requesting vaccine but not being able to receive it, primarily due to vaccine unavailability.

About one-fourth of the total number of those responding to the survey indicated they declined the vaccine when it was offered to them. Reasons offered by those respondents include thinking the vaccination was unnecessary, or that receiving it would make them ill.

Jones, Schaffner and the study's other authors — Amanda Ingram, an epidemiologist with the State Department of Health, and Allen S. Craig, M.D., state epidemiologist for Communicable and Environmental Disease Services at the Tennessee Department of Health and assistant clinical professor of Preventive Medicine at VUMC — conclude there are still significant barriers contributing to the varying rates of influenza vaccination. Inadequate vaccine supply is only one component of the problem.

Other persisting problems are myths about the safety or possible side-effects associated with influenza vaccines.

“I think the study highlights the fact that there remain important groups that still have far lower rates of influenza immunization than they should, and unfortunately that includes health care providers. If for no other reason, health care providers need to be immunized to protect their patients,” Jones said.