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. 2022 Jun 16:77:100068.
doi: 10.1016/j.clinsp.2022.100068. eCollection 2022.

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

Lucy Santos Villas-Boas  1 , Anderson Vicente de Paula  1 , Almir Ribeiro da Silva Jr  1 , Heuder Gustavo Oliveira Paiao  1 , Tania Regina Tozetto-Mendoza  1 , Erika Regina Manuli  2 , Fábio Eudes Leal  3 , Andrea de Barros Coscelli Ferraz  3 , Ester Cerdeira Sabino  4 , Ana Luiza Bierrenbach  5 , Steven Sol Witkin  6 , Maria Cassia Mendes-Correa  7
Affiliations

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

Lucy Santos Villas-Boas et al. Clinics (Sao Paulo). .

Abstract

Objectives: The aim of the present study was to evaluate if neutralizing antibody responses induced by infection with the SARS-CoV-2 strain that was dominant at the beginning of the pandemic or by the Gamma variant was effective against the Omicron variant.

Methods: Convalescent sera from 109 individuals, never exposed to a SARS-CoV-2 vaccine, who had mild or moderate symptoms not requiring hospitalization following either a documented SARS-CoV-2 ancestral strain infection or a Gamma variant infection, were assayed for in vitro neutralizing antibody activity against their original strains and the Omicron variant.

Results: Following an infection with the ancestral strain, 56 (93.3%), 45 (77.6%) and 1 (1.7%) serum sample were positive for neutralizing antibodies against the ancestral, Gamma variant, and Omicron variant, respectively. After infection with the Gamma variant, 43 (87.8%) and 2 (4.1%) sera were positive for neutralizing antibodies against the Gamma and Omicron variants, respectively.

Conclusions: Neutralizing antibodies generated following mild or moderate infection with the SARS-CoV-2 ancestral strain or the Gamma variant are not protective against the Omicron variant.

Keywords: Gamma variant; Neutralizing antibodies; Omicron variant; Protective antibodies; SARS-CoV-2.

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Conflict of interest statement

Declaration of Competing Interest The authors declare no conflicts of interest.

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Supplementary concepts