An Analysis of the Neutralizing Antibodies against the Main SARS-CoV-2 Variants in Healthcare Workers (HCWs) Vaccinated against or Infected by SARS-CoV-2.

Although the anti-COVID-19 vaccination has proved to be an effective preventive tool, "breakthrough infections" have been documented in patients with complete primary vaccination courses. Most of the SARS-CoV-2 neutralizing antibodies produced after SARS-CoV-2 infection target the spike protein receptor-binding domain which has an important role in facilitating viral entry and the infection of the host cells. SARS-CoV-2 has demonstrated the ability to evolve by accumulating mutations in the spike protein to escape the humoral response of a host. The aim of this study was to compare the titers of neutralizing antibodies (NtAbs) against the variants of SARS-CoV-2 by analyzing the sera of recovered and vaccinated healthcare workers (HCWs). A total of 293 HCWs were enrolled and divided into three cohorts as follows: 91 who had recovered from SARS-CoV-2 infection (nVP); 102 that were vaccinated and became positive after the primary cycle (VP); and 100 that were vaccinated with complete primary cycles and concluded the follow-up period without becoming positive (VN). Higher neutralization titers were observed in the vaccinated subjects' arms compared to the nVP subjects' arms. Differences in neutralization titers between arms for single variants were statistically highly significant (