Backward Bifurcation and Optimal Control in an Age-Structured SVI Epidemic Model. European Journal of Pure and Applied Mathematics, Maryland, USA, v. 18, n. 4, p. 6775, 2025. DOI: 10.29020/nybg.ejpam.v18i4.6775. Disponível em: https://www.ejpam.com/index.php/ejpam/article/view/6775. Acesso em: 5 dec. 2025.