An analysis of the association between influenza coverage and outbreak across demographic factors in the United States

Open Access
Zomorodi, Naseem
Area of Honors:
Bachelor of Science
Document Type:
Thesis Supervisors:
  • Dr. Shirley Clark, Thesis Supervisor
  • Dr. Ronald Walker, Faculty Reader
  • Michael J Chorney, Honors Advisor
  • influenza
  • vaccination coverage
  • vaccine
  • disease outbreak
Despite the annual disease and economic burden of the influenza virus, just over 40% of American adults and slightly over 60% of American children receive the annual influenza vaccination. In 2009, in addition to the annual influenza season, a H1N1 (swine flu) pandemic occurred, resulting in a second potential immunization and a heightened awareness of the dangers of influenza. The purpose of this study was to determine how state-level demographic factors were associated with vaccination coverage rates in the four years following the 2009 H1N1 influenza pandemic, as well as to determine if there is a relationship between vaccination coverage rates and disease outbreak. In regards to educational status, the results showed that the percentage of people not having graduated high school was negatively associated with vaccination rates for all flu seasons except 2011-2012, and having a high school education or higher was positively correlated with vaccination rates in all seasons except 2012-2013. The percentage of people listed as employed was positively correlated with vaccination rates for all seasons except 2011-2012, while being unemployed was negatively correlated with vaccination rates for all seasons. In terms of socioeconomic status, the percentage of people in poverty was negatively correlated with vaccination rates, and median family income was positively correlated with vaccination rates during all flu seasons studied except 2011-2012. These findings were consistent with a number of previous case studies examining how demographic factors relate to vaccination coverage rates. Almost all comparisons of race and vaccination coverage rates were statistically insignificant. During only the 2009-2010 flu season, increased vaccination rates were associated with a decreased number of weeks of high influenza activity. Increased vaccination rates during the 2010-2011 and 2012-2013 flu seasons were correlated with higher mortality rates, which may indicate that national influenza vaccination rates are not an accurate predictor of the magnitude of disease burden that impacts the healthcare system for that year. There are no readily available accurate measures of the influenza incidence in the general population that does not use any medical services. It is assumed that the mortality rates and numbers of high-incidence weeks are indicative of the impact in the general population but this is not confirmed. This lack of correlation may be a result of the vaccine effectiveness, which, for the influenza vaccine, often is around 45 – 60% in any given year. A review of the state flu incidence data did show that the elderly and pediatric populations are disproportionately affected. In order to improve vaccine coverage to rates that are believed to convey herd immunity, the Centers for Disease Prevention and Control (CDC) creates campaigns to promote safe health practices and vaccination, some of which target groups at risk and groups less likely to immunize. As noted in the literature, challenges to reducing influenza in America include the perception that influenza is not harmful, a distrust of the medical community, not vaccinating up to herd immunity levels, and the low relative vaccine effectiveness of the influenza vaccination. This national data analysis confirmed the literature case studies and surveys regarding the vaccination rates in communities with these perceptions and challenges. Additional investigation is required to further elucidate the effectiveness of messaging campaigns in reducing influenza outbreak in America and if needed, reaching out into the community in novel ways to improve vaccination rates.