ANN ARBOR—When a new strain of influenza began to sicken even healthy younger adults three years ago, public interest in getting the newly developed H1N1 vaccine started strong but declined over time even as more people were getting sick, a new study shows.

Researchers at RAND Corp. and the University of Michigan found that the more the public learned about this new type of influenza and the longer they had to wait for the vaccine, the less interested they were in getting it.

“Our results provide further evidence of how important it is to develop technology to speed vaccine production,” said the study’s co-author, Brian Zikmund-Fisher, an assistant professor in the U-M School of Public Health. “Many more people would have been interested in vaccination had the vaccine been available even three months earlier.”

The study, a collaboration between Zikmund-Fisher and Courtney Gidengil and Andrew Parker of the RAND Corp, is being released today (Feb. 16) for advance online viewing by the American Journal of Public Health.

Each year the strains of influenza circling the world change slightly. Occasionally a new strain emerges, as happened in March 2009 with the H1N1 virus. Later that spring the World Health Organization declared a level 6 pandemic, the highest level possible, which meant that the disease had spread worldwide. In the United States, the peak rate of infections and hospitalizations from H1N1 occurred between September and December 2009.

While other research has looked at people’s beliefs about the H1N1 influenza at one point at time, this study used the RAND American Life Panel, a large national sample, to track both the public’s perceived risk of catching H1N1 and their intention of receiving the new vaccine over time. The authors gathered data 10 different times from May 2009 (when HIN1 illnesses were still very rare) until January 2010 (when the worst of the pandemic had passed in the United States). The vaccine came out in October 2009, was widely available by November.

The U-M and RAND study found that intention to get vaccinated dropped from 50 percent in May 2009 when news of H1N1 first surfaced but the vaccine was not available to just 16 percent of unvaccinated people by January, when the last survey was given.

The authors’ findings are consistent with the fact that by December 2009, only 24 percent of the entire U.S. population received the H1N1 vaccine. Fortunately the 2009 H1N1 strain was not particularly deadly.

The study also found that those who received a seasonal influenza vaccine the previous year were more likely to get the new H1N1 vaccine during the pandemic. This is important, the study’s authors note, because it suggests that encouraging regular seasonal flu vaccination is a valuable part of preparing for future pandemics.

One other interesting finding was that those with lower income or education tended to believe they were at higher risk for catching H1N1 but were nonetheless less likely to want to get the vaccine. Zikmund-Fisher and his colleagues speculated that these groups may have a higher level of mistrust of new vaccines.

The U-M and RAND researchers hope their study will be used to better understand what motivates the public to seek vaccinations, which will ultimately save lives when the next pandemic strikes.

In addition to SPH’s Department of Health Behavior and Health Education, Zikmund-Fisher also has appointments in the Department of Internal Medicine, the Center for Bioethics and Social Sciences in Medicine and the Risk Science Center. Gidengil is at the RAND Corporation in Boston and Parker is with the RAND Corporation in Pittsburgh.

The complete study, called “Trends in Risk Perceptions and Vaccination Intentions: A Longitudinal Study of the First Year of the H1N1 Pandemic,” will be published in the April 2012 edition of the American Journal of Public Health and is available for advance, online viewing at www.ajph.org.

Related Links:

• Brian Zikmund-Fisher
• School of Public Health