Katawa, G. et al. 2021. Systematic Review on COVID-19 Vaccines: Comparative Study of AstraZeneca, Pfizer-BioNTech, Sputnik V, Johnson & Johnson, Moderna and Corona Vac. International Journal of Innovative Research in Medical Science. 6, 11 (Nov. 2021), 784–794. DOI:https://doi.org/10.23958/ijirms/vol06-i11/1250.