Random vaccine distribution prevents spread of disease: Study

Jul 30 2010

The best way to prevent the spread of disease in rural areas may be by targeting select popular hangouts, according to a new study by the Kansas State University EpiCenter research team.

The team published "Efficient Mitigation Strategies for Epidemics in Rural Regions" in the July edition of the journal PLoS ONE. The study looks at mitigation strategies based on a contact network model developed using information collected from residents in Clay County, Kan.

The team used surveys, both mailed and conducted in person, to get data on people who have a high rate of contact with other people and to find the most frequently visited locations in Clay County. The survey had a 65 percent response rate.

The study found that random vaccine distribution in selected popular locations in a rural community can reach the people who play active roles in spreading a disease like H1N1, said team member Caterina Scoglio, K-State associate professor of electrical and computer engineering.

"Our simulations show that the targeted vaccinations of only 10 percent of the sampled population reduced the size of the epidemic by 34.5 percent," Scoglio said. "Additionally, if 10 percent of the population visiting one of the most popular locations is randomly vaccinated, the epidemic size is reduced by 19 percent." According to Scoglio, the results suggest a new, highly effective implementation strategy for targeting vaccinations based on popular locations in rural communities.

One the biggest challenges in the computation of the simulated outbreak scenarios was to create a new mathematical expression for the level of contact among people from the collected data, said Phillip Schumm, K-State graduate student in electrical engineering and a team member.

"Formulas in the current literature were not adequate to correctly express the whole range of our collected information, so to fit our purpose we created a new expression for the level of contact," he said.

The survey identified four measures of risk factors important to the spread of epidemics in rural regions: health risk -- people with existing health conditions; contact risk -- the number of a people one person comes in contact with; prevention risk -- people who have not been vaccinated for a particular disease; and compliance risk -- people who continue social contacts even during an epidemic.

"All these risks tended to co-occur. If someone had a high risk in one category, they were likely to have a high risk in all the others," said team member Walter Schumm, professor of family studies and human services. "The people with the most contacts tended to have the least preparedness for an epidemic, and people who were willing to visit others even during an epidemic were among those most at-risk because of their health status. People who tended to visit friends and family members more often during normal times also were likely to retain this behavior even under epidemic conditions."

The survey found the most frequented locations were a grocery store, fast-food restaurant and discount store in Clay Center.

"This tells us that health campaigns on how to limit the spread of disease would be good in these places, as well as making them available to provide vaccinations," Scoglio said.

The research team also included Todd Easton, associate professor of industrial and manufacturing systems engineering, and Sohini Roy Chowdhury, Ali Sydney and Mina Youssef, all K-State graduate students in electrical engineering. The National Science Foundation funded the work through K-State's EpiCenter, also known as the Center for Complex Network Approach to Epidemic Modeling and Simulation.

Schumm said the survey approach is a cost-effective way for other communities to replicate and develop their own strategies for mitigating the spread of disease. "Having their own plans is important," he said. "Research has shown mitigation strategies used in urban areas are not as effective in rural areas because of differences in population and contact patterns."

New research initiatives at the EpiCenter include a study supported by K-State's Center for Engagement and Community Development, where the group is conducting a similar survey campaign in Chanute and Neosho County, Kan.

"The Chanute survey is taking a more zoonotic approach," Scoglio said. "We've teamed up with K-State's Center for Excellence in Emerging and Zoonotic Diseases and the National Agricultural Biosecurity Center. As a consequence, our new surveys ask questions about how much contact residents have with domestic animals, livestock and wildlife."

"The survey also delves more deeply into respondents' health, asking if they got a flu shot and if they take supplements like zinc and vitamin D to see if there are any correlations in flu prevention," Schumm said. "The surveys are also finding out what time of day people are most likely to visit the community's most popular locations and how many people they come in close contact with there."