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 - Villas-Boas, Lucy Santos; Paula, Anderson Vicente de; Silva, Almir Ribeiro da; Paiao, Heuder Gustavo Oliveira; Mendoza, Tânia Regina Tozetto; Manuli, Erika Regina; Leal, Fabio Eudes; Ferraz, Andrea de Barros Coscelli; Sabino, Ester Cerdeira; Correa, Maria Cássia Jacintho Mendes (Clinics, 2022)