Alotaibi, A., S. S. Almudarra, H. S. . Algarni, Y. Bakhsh, Z. M. E. Dafaalla, N. A. Alhowail, and A. M. Assiri. “Adherence to Vaccine Requirements Among Hajj Pilgrims in Saudi Arabia, 2017-2019”. Tropical Health and Medical Research, vol. 3, no. 2, Aug. 2021, pp. 86-97, doi:10.35916/thmr.v3i2.54.