Modeling the Impact of Susceptibility Heterogeneity in Diphtheria Outbreaks within a Vaccinated Population Using Fractional-Order Dynamics. JPRM [Internet]. 2026 Jun. 10 [cited 2026 Jun. 10];22(2):50-81. Available from: https://jprm.sms.edu.pk/index.php/jprm/article/view/458