“Absence of Neutralizing Antibodies Against the Omicron SARS-CoV-2 Variant in Convalescent Sera from Individuals Infected With the Ancestral SARS-CoV-2 Virus or Its Gamma Variant”. Clinics, vol. 77, June 2022, p. 100068, https://doi.org/10.1016/j.clinsp.2022.100068.