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

EBERHARDT, A. T.; SIMONCINI, M. ; PIÑA, C.; GALOPPO, G.

EPIDEMIOLOGY AND INFECTION.

CAMBRIDGE UNIV PRESS

Lugar: Cambridge; Año: 2022 vol. 19

0950-2688

The SARS-CoV-2 Omicron variant has increased infectivity and immune escape compared withprevious variants, and caused the surge of massive COVID-19 waves globally. Despite a vastmajority (~90%) of the population of Santa Fe city, Argentina, had been vaccinated and/or hadbeen infected by SARS-CoV-2 when Omicron emerged, the epidemic wave that followed itsarrival 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 toconduct a longitudinal study to provide individual-level real-world data linking antibody levelsand protection against COVID-19 during the wave. A very large proportion of 1455 sampledindividuals had immunological memory against COVID-19 at the arrival of Omicron (almost90%), and about half (48.9%) had high anti-Spike IgG levels (>200 UI/ml). However, theantibody titres varied greatly among the participants, and such variability depended mainly onthe vaccine platform received, on having had COVID-19 previously and on the number of dayselapsed since last antigen exposure (vaccine shot or natural infection). Following up 514participants provided real-world evidence of antibody-mediated protection against COVID-19during 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 andseverity of symptoms during the wave. Also, receiving a vaccine shot during the follow-upperiod reduced the COVID-19 risk drastically (15-fold). These results highlight the importanceof maintaining high defences through vaccination at times of high risk of exposure to immuneescaping variants.