Long-Term Analysis of Antibodies Elicited by Sputnik V in Tucuman, Argentina

Background: Gam-COVID-Vac, also known as SPUTNIK V, is the first COVID-19 vaccine registered, has emergency use authorization in 70 nations, and has been administered to millions worldwide. However, there are very few peer-reviewed studies describing its effects. As independent reports begin to be published, a more accurate picture regarding safety and effectiveness could accelerate approval by the WHO. Methods: An ELISA that detects anti-SARS-CoV-2-spike-RBD IgG was used, in both transversal and longitudinal studies, to analyze humoral immune responses in 602 healthcare workers who received SPUTNIK V between December 2020 and July 2021.Findings: Seroconversion was detected in 97% of individuals after 28 days post-vaccination (dpv). Anti-RBD titers began to decrease after 60 dpv, but remained detectable in 94% of volunteers at 90 dpv. At 180 dpv, anti-RDB titers persisted in 31% of volunteers. Previous SARS-CoV-2 infection triggered increased immune response to the first dose, and increased neutralization activity against different variants of concern. The second dose in previously infected individuals further increased anti-RBD titers, even after 90 dpv. However, not all individuals with previous infection responded equally, as only those with basal titers above a certain threshold showed robust responses. Time elapsed between COVID-19 diagnosis and vaccination did not influence titers elicited. Interpretation: Data presented herein provides essential knowledge regarding the kinetics of antibodies induced by SPUTNIK V up to six months after immunization, and suggests that when considering one-dose vaccination policies for individuals with previous SARS-CoV-2 infection, serological studies to determine basal titers may be important, independent of when diagnosis occurred. Funding Statement: This research was supported by the Ministry of Public Health of Tucuman (Argentina), Argentinean Research Council-CONICET (PIP 722 and 806), Argentinean Research Agency-MINCYT grants (PICT-2018-3379 and PICT2018-02989), National University of Tucuman (PIUNT-UNT D644/1 and D624), and Florencio Fiorini Foundation. Declaration of Interests: B. L. is a named inventor on a patent filed by the Icahn School of Medicine which includes the 293T-ACE2-TMPRSS2 (F8-2) cells used for the virus neutralization assay. All other have nothing to declare. Ethics Approval Statement: Protocols were approved by the regional ethics research boards (Ex. N° 3929-410-P-2020), following the Declaration of Helsinki. Personal data from all volunteers were encrypted. Eligibility criteria were age between 18 to 60 years without any COVID-19 symptoms at the time of vaccination. Individuals provided a signed informed consent to be included in the database of the present study.