Association of Lower Antispike Antibody Levels with Mortality in ICU Patients with COVID-19 Disease

Though vaccines have been reported as highly efficacious in preventing severe COVID-19 disease, there is emerging data of severe infections, albeit a small number, in vaccinated individuals. We have conducted a retrospective observational study to assess the clinical characteristics, immunological response, and disease outcomes among the vaccinated and unvaccinated patients admitted to the ICU with severe COVID-19 disease.

Study Design and Participants. We conducted a retrospective observational study in COVID ICU of a tertiary care hospital. Data were collected from the month of 1 April 2021 to 31 November 2021. All adult patients admitted to the ICU having severe COVID-19 disease were included in the study. Data were collected from the medical records database which included demographics, a clinical course in the ICU, laboratory and radiological parameters, and disease outcomes. In a subset of patients, cell-mediated immunity and S1S2-neutralising antibody assessment was done.

A total of 419 patients with severe COVID-19 were included in the study. Of the 419 patients, 90 (21.5%) were vaccinated, and 329 (78.5%) were unvaccinated. There was a significantly higher mortality in unvaccinated severe COVID 19 patients as compared to vaccinated severe COVID patients (46.2% vs 34.4%; P < 0.0455). The neutralizing antibody titre was significantly higher in survivors as compared to nonsurvivors (2139.8, SE ± 713.3 vs 471, SE ± 154.4); P < 0.026.

Our study suggests the association of lower neutralizing antibody levels with mortality in ICU patients admitted with COVID-19 breakthrough infections.