Preceding anti-spike IgG levels predicted risk and severity of COVID-19 during the Omicron-dominant wave in Santa Fe city, Argentina

EBERHARDT, AYELEN T.; SIMONCINI, MELINA; PINÃ, CARLOS; GALOPPO, GERMÁN; PARACHÚ-MARCO, VIRGINIA; RACCA, ANDREA; ARCE, SOFIÁ; VIOTTO, EVANGELINA; FACELLI, FLORENCIA; VALLI, FLORENCIA; BOTTO, CECILIA; SCARPA, LEONARDO; JUNGES, CELINA; PALAVECINO, CINTIA; BECCARIA, CAMILA; SKLAR, DIEGO; MINGO, GRACIELA; GENOLET, ALICIA; MUNÕZ DE TORO, MÓNICA; AIMAR, HUGO; MARIGNAC, VERÓNICA; BOSSIO, JUAN CARLOS; ARMANDO, GUSTAVO; FERNÁNDEZ, HUGO; BELDOMENICO, PABLO M.

EPIDEMIOLOGY AND INFECTION.

CAMBRIDGE UNIV PRESS

Año: 2022 vol. 150

0950-2688

The SARS-CoV-2 Omicron variant has increased infectivity and immune escape compared with previous variants, and caused the surge of massive COVID-19 waves globally. Despite a vast majority (~90%) of the population of Santa Fe city, Argentina had been vaccinated and/or had been infected by SARS-CoV-2 when Omicron emerged, the epidemic wave that followed its arrival was by far the largest one experienced in the city. A serosurvey conducted prior to the arrival of Omicron allowed to assess the acquired humoral defences preceding the wave and to conduct a longitudinal study to provide individual-level real-world data linking antibody levels and protection against COVID-19 during the wave. A very large proportion of 1455 sampled individuals had immunological memory against COVID-19 at the arrival of Omicron (almost 90%), and about half (48.9%) had high anti-spike immunoglobulin G levels (>200 UI/ml). However, the antibody titres varied greatly among the participants, and such variability depended mainly on the vaccine platform received, on having had COVID-19 previously and on the number of days elapsed since last antigen exposure (vaccine shot or natural infection). A follow-up of 514 participants provided real-world evidence of antibody-mediated protection against COVID-19 during a period of high risk of exposure to an immune-escaping highly transmissible variant. Pre-wave antibody titres were strongly negatively associated with COVID-19 incidence and severity of symptoms during the wave. Also, receiving a vaccine shot during the follow-up period reduced the COVID-19 risk drastically (15-fold). These results highlight the importance of maintaining high defences through vaccination at times of high risk of exposure to immune-escaping variants.