ANN ARBOR, Mich., Nov. 2 (UPI) -- U.S. medical researchers suggest whooping cough -- pertussis -- immunity may last at least 30 years on average.
The study, published in the journal PLoS Pathogens, used mathematical models to test the theory whooping cough has been on the rise due to waning immunity in vaccinated or previously exposed people.
Pejman Rohani of the University of Michigan in Ann Arbor, but based at the University of Georgia during completion of the study, and Helen Wearing of the University of New Mexico in Albuquerque constructed two different mathematical models based on immunity "extinctions."
They compared predictions to incidence data from England and Wales from both the pre-vaccine era -- 1945-1957 -- and the vaccine era --1958-1972 and found, on average, whooping cough immunity lasts at least 30 years and perhaps as long as 70 years after natural infection.
"This is surprising because clinical epidemiologists currently believe the duration of pertussis immunity is somewhere between 4-20 years," Rohani says in a statement.
However, Rohani points out that in the past 20 years or so, vaccines have quite fundamentally changed and stimulate a different part of the immune system -- especially in North America.