Helen Wearing

“There’s been a lot of interest in the United States and other countries about the resurgence of whooping cough cases,” said Helen Wearing, UNM biology and mathematics assistant professor and lead author on the paper published Oct. 23 in the open-access journal PLoS Pathogens. “Using mathematical models, we discovered that immunity from natural infection can be long lasting. ”

"This is surprising because clinical epidemiologists currently believe the duration of pertussis immunity is somewhere between four and 20 years," said UM’s Pejman Rohani, professor of ecology and evolutionary biology.

Several explanations have been proposed for the surprising increase in cases, and one leading idea is that the immunity enjoyed by vaccinated or previously exposed people is simply wearing off. It's been documented that in some individuals immunity has waned over time, but the exact details of how long protection typically lasts and how its waning affects disease transmission have not been clear.

Wearing and Rohani took a mathematical approach, using models to explore various scenarios and comparing the predictions generated by those models to data on whooping cough incidence. The researchers constructed two models, a basic model and an immune-boosting model, with different assumptions about what happens when a person whose immunity has lapsed is exposed to pertussis and how much that person contributes to transmission. [MORE