Quantitative analysis of anti-Spike antibodies against SARS-CoV-2 in vaccinated and non-vaccinated patients.

Abstract

Introduction: The vaccination campaign against the SARS-CoV-2 virus began at the end of 2020. The first vaccines applied were Sputnik V, AstraZeneca and Sinopharm, with efficacies of 97.6 %, 66.7 % and 79.3 % respectively. Objectives: We performed a comparison of total anti-spike antibody concentrations in unvaccinated people and people vaccinated with the first dose and second dose, in both infected and uninfected patients. Materials and methods: A total of 1567 samples from patients who attended our laboratory (Laboratorio de Análisis Clínicos Buenos Aires, Argentina) during 2021 were analyzed. Patients were classified into groups according to the dose, type of vaccine received and infection status. Results: The median antibodies of the unvaccinated patients and those vaccinated with a single dose were: 250.0 U/  ml Vaccinated Infected, 90.6 U/ml Vaccinated Not Infected, 51.9 U/ml Not Vaccinated Infected and 0.4 U/ ml Not Vaccinated Not Infected. All patients vaccinated with the first dose and infected reached a concentration of 250.0 U/ml. Those not infected presented differences according to the type of vaccine received [Sputnik V (114.2 U/ml), AstraZeneca (35.4 U/ml), Sinopharm (16.6 U/ml)]. The subgroups with two doses reached a concentration of 250.0 U/ml, except those uninfected vaccinated with Sinopharm/Sinopharm (113.4 U/ml). Conclusion: All SARS-CoV-2-infected patients receiving any vaccine showed higher anti-spike antibody levels than the vaccinated uninfected group. Patients immunized with a single dose who did not develop the infection presented significant differences in the concentration of antibodies depending on the vaccine administered. In contrast, the whole population who completed the two-dose schedule, regardless of the infection status and the scheme applied, reached the maximum concentration of antibodies except with the Sinopharm/Sinopharm combination.