The human factor involves two biological characteristics, "memory and how adaptable people can be," Blower said. "These characteristics drive human behavior."
Blower and her group used people's attitudes toward the seasonal flu to construct their model. With seasonal flu, protective immunity ?a flu shot ?lasts only one year. Thus, individuals must decide each year whether or not to participate in a vaccination program.
The model Blower's team developed is inspired by game theory, used in economics to predict how non-communicating, selfish individuals reach a collective behavior with respect to a common dilemma by adapting to what they think are other people's decisions. The group modeled each individual's strategy for making yearly vaccination decisions as an adaptive process of trial and error. They tracked both individual-level decisions and population-level variables ?that is, the yearly vaccine coverage level and influenza prevalence, where prevalence is defined as the proportion of the population that is infected. The individual-level model was based on the human biological attributes of memory and adaptability.
"We assume that the decision of each individual is based upon self-interest, that people wish to avoid coming down with the flu, preferably without having to vaccinate," said Breban.
It is the adaptive decision-making by the individual, the researchers say, that may be an important and previously overlooked causal factor in driving influenza epidemiology.
"Including cognitive and personality factors into epidemic models can dramatically change our understanding of why flu epidemics occur." said Vardavas.