Generally, pathogen prevalence is a more accesible metric for users, but the Imperial equilibrium function requires an annual EIR. This function converts a given pathogen prevalence to an EIR
convert_prevalence_to_eir(prevalence, age_vector, ft, params)
a vector of the equilibrium number of humans in each SIS stage
desired prevalence value
age distribution of the population
proportion treated
entomological and epidemiological parameters