More work is needed to find the causes of flu vaccine disparities for the elderly

Byung-Kwang Yoo Byung-Kwang Yoo

Published online today in the journal Vaccine, the outcome highlights the need to identify the unique causes of racial and ethnic disparities in flu vaccination rates among those who are 65 years of age and older.

“Until we know the reasons behind a disparity, we can’t eliminate it,” said Byung-Kwang Yoo, associate professor of public health sciences at UC Davis and lead author of the study. “Older Americans are most likely to suffer flu complications such as pneumonia and death. Increasing vaccination rates among all of them should be a priority.”

In conducting the study, the researchers used 2010-2011 data from the Medicare Current Beneficiary Survey, a nationally representative sample of the Medicare population. They applied a statistical technique known as the Oaxaca-Blinder decomposition method, commonly used to evaluate labor market discrimination, to determine the potential impact that specific factors could have on closing gaps in vaccination rates between whites (who had a 76 percent vaccination rate) and two other groups: non-Hispanic African Americans (who had a 62 percent vaccination rate) and non-English-speaking Hispanics (who had a 50 percent vaccination rate). English-speaking Hispanics were excluded, as the disparity between this group and whites was not significant.

“This method has not been used frequently in the medical field, but we knew it could be useful for analyzing factors that cause health disparities,” said Peter Szilagyi, the study’s senior author and professor and vice-chair for clinical research at Mattel Children’s Hospital UCLA.

In addition to supplemental insurance coverage and having a regular doctor, Yoo and Szilagyi considered 15 additional characteristics often associated with racial and ethnic disparities, including type of supplemental insurance, education, health status, geographic location and household size. Their results showed that the maximum combined impact all 17 characteristics could have on reducing the disparities was just 45 percent.

“To truly have an equalizing effect, we expect this number to be much higher — at least 90 percent,” Yoo said.

Peter Szilagyi Photograph courtesy of UCLA
Peter Szilagyi

Szilagyi added, “Our paper demonstrates that we can chip away at the problem by raising the proportion of Americans with a regular physician and with adequate health insurance coverage and by optimizing delivery of influenza vaccinations within primary care practices, but more research is needed to uncover factors leading to these disparities.”

For next steps, Yoo recommends fully mining the reasons behind increases in flu vaccination rates and decreases in disparities for other populations, including children.

“Finding out what worked for others could give us a new arsenal of factors to test and then put into use in finally eliminating flu vaccine disparities for the elderly,” Yoo said.

Yoo and Szilagyi’s co-author on the study was Takuya Hasebe, a former UC Davis postdoctoral researcher who is currently at Sophia University in Tokyo. Their work was funded by the National Institutes of Health (grant R03AG042646).

Copies of the study, titled “Decomposing Racial/Ethnic Disparities in Influenza Vaccination among the Elderly” (DOI 10.1016/j.vaccine.2015.03.054) are available to credentialed journalists upon request. Please contact Elsevier’s Newsroom at [email protected] or +31 20 4853564.

More information about UC Davis Health System is at and about UCLA Health System is at

Vaccine is the pre-eminent journal for those interested in vaccines and vaccination. It is the official journal of The Edward Jenner Society, The International Society for Vaccines and The Japanese Society for Vaccinology and is published by Elsevier:

Categories Flu