SALLAM, Malik et al. Willingness-to-pay for COVID-19 vaccine in ten low-middle-income countries in Asia, Africa and South America: A cross-sectional study . Narra J, [S. l.], v. 2, n. 1, 2022. DOI: 10.52225/narra.v2i1.74. Disponível em: https://www.narraj.org/main/article/view/74. Acesso em: 18 mar. 2026.