Researchers Find the Strongest Determinants of Getting a Flu Shot


In a new study assessing the demographics of the groups less likely to receive the flu shot, researchers find the biggest determinants of whether an individual was vaccinated for the flu.

In a new study assessing the demographics of the groups less likely to receive the flu shot, researchers found that age, insurance status, and having a personal physician were among the biggest determinants of whether an individual was vaccinated for the flu.

The study, published in the Journal of General Internal Medicine, analyzed data from self-reported flu vaccination rates in 2018, which included data from both the 2017-18 flu season and 2018-19 season. These data had been recorded in the Behavioral Risk Factor Surveillance System, which is an annual survey conducted by state health departments and the CDC every year.

"To achieve herd immunity, we would need to reach about an 80% vaccination rate, but no subgroup in our study exceeded 60%," said senior author R. Adams Dudley, MD, MBA, of the UCSF Philip R. Lee Institute for Health Policy Studies and School of Medicine; and University of Minnesota Medical School and Institute for Health Informatics, in a press release. "While social distancing, mask-wearing, and staying away from crowds will mitigate the spread of the flu, a dangerous type of the flu—such as the Spanish flu of 1918—could result in more than 61,000 fatalities."

In the study, the researchers found that 22.6% of surveyed individuals aged 18 to 24 years received the flu vaccine, whereas 59.3% of individuals over the age of 75 received the vaccine. For those without insurance, 16.1% were vaccinated, whereas 41.6% of individuals with insurance were vaccinated. Additionally, patients without a personal physician were vaccinated at a rate of 19.4%, whereas those with a personal physician were vaccinated at a rate of 43.6%.

Not having a chronic condition also lowered the rate of vaccination, as 31.6% of those with no chronic condition were vaccinated, whereas 52.7% of those with 4 or more chronic conditions were vaccinated.

Variation by income was much smaller in contrast, as 33.9% of those in a household with an income lower than $15,000 were vaccinated, whereas 41.8% of those in a household with an income more than $50,000 were vaccinated.

By state, immunization rates were found to be lowest in Texas at 26.4% and highest in Washington, DC, at 44.2%. Other states that had lower rates included Louisiana (26.4%), New York (28%), Indiana (28.5%), and Tennessee (28.6%). States with higher rates included West Virginia (42.6%), North Carolina (41.7%), Iowa (40.6%), and Pennsylvania (40.3%). California was in the middle at 32.4%.

Additionally, the researchers found the immunization rates to be lower among Black (33.9%) and Hispanic (28.9%) populations than among White (41.5%) and Asian populations (38.3%). Men were also less likely to get vaccinated at a rate of 36.7% compared with women, who were vaccinated at a rate of 41.6%.

In order to manage this dilemma as the flu season approaches, long- and short-term interventions will be needed, according to first author of the study Brandon Yan, a third-year medical student at University of California, San Francisco.

"We need a concerted public health campaign that includes public health officials, health care providers, and local communities, and reaches those groups most at risk for not getting vaccinated. And we need a proactive primary care outreach strategy to address patient concerns and provide information on how and where to get vaccinated," Yan said in the press release.

In the long-term, the solution may be to examine how to make vaccines more accessible, such as by increasing their availability in retail pharmacies and making them free for uninsured individuals.

"The ongoing pandemic also raises the issue of whether the flu vaccine and the future COVID-19 vaccine should be mandated," Yan said. "While a federal mandate may be difficult politically, private organizations like colleges and employers could make attendance and employment contingent on getting up-to-date with vaccines."


COVID-19 vaccines are moving fast, but will Americans agree to get them? San Francisco, CA: University of California - San Francisco; August 26, 2020. Accessed September 1, 2020.

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