U. ROCHESTER (US) — Disparities in flu vaccination rates based on race, ethnicity, and age grow even larger in years when the vaccine supply is limited or delayed.
A study published in the American Journal of Preventive Medicine found that the gap in seasonal influenza vaccination rates for African Americans, Hispanics, and people over the age of 65 grew by as much as 7 percent in years when there were supply issues.
By contrast, the gap narrowed by as much as 11 percentage points during years when the supply was more timely and abundant.
Disparities in immunization rates are a persistent public health challenge with serious consequences, considering influenza is one of the leading causes of death among people 65 and older.
“There is a strong association between influenza vaccine supply and the gap in vaccination rates between racial and ethnic groups,” says Byung-Kwang Yoo, the study’s lead author and an assistant professor of community and preventive medicine at the University of Rochester. “These disparities are aggravated when vaccine supply is delayed or decreased.”
Using data from the Medicare Current Beneficiary Survey, which consists of claims data and survey results of individual Medicare recipients, researchers looked at seasonal influenza vaccination rates from 2000 to 2005. The data was broken into four “periods” consisting of two concurrent flu seasons during which the same group of individuals was followed for each period. For example, the same group of respondents was followed for the 2000-2001 and 2001-2002 vaccine seasons.
This method allowed researchers to compare individual activity during years in which vaccine supply fluctuated. The 2000-2001 and 2004-2005 seasons where characterized by severe vaccine shortages, 2001-2002 and 2003-2004 saw moderate shortages, and there were no supply problems during the 2002-2003 season.
Overall vaccinate rates among non-Hispanic whites ranged from 71 to 78 percent during the study period, significantly higher than African American (43-63 percent).
Total vaccination rates were also lower among Hispanics, who were categorized into English- and Spanish-speaking groups depending upon the language used to respond to the survey. Vaccination rates for English-speaking Hispanics were 58-75 percent and rates for the Spanish-speaking group were 31-53 percent, the lowest among the groups studied.
In years when there were problems with vaccine supply, the gap in vaccination rates between whites and the other groups jumped by 2 to 7 percentage points, depending upon the severity of the shortage. When flu seasons with supply problems were followed by seasons with adequate vaccine supply, the gap between the groups would narrow by 2 to 11 percentage points.
The authors speculate that the sharper decline in vaccination rates among minorities is attributed to a number of factors including more pronounced vaccine shortages among providers in under-served communities and, in the case of Spanish-speaking populations, language barriers.
The researchers recommend a more concerted effort to ensure clinics that serve vulnerable populations are prioritized for vaccine supply and that the government help mitigate the financial risk for these providers by covering the cost of purchasing the vaccines. They also recommend more broad-based and multilingual communication and outreach efforts.
The study was funded by the National Institute of Allergy and Infectious Diseases.
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