Introduction: During the last two and a half years, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has spread around the world. Most of the SARS-CoV-2 vaccines are
designed to produce anti-SARS-CoV-2 immunoglobulin G (IgG) against the viral S-glycoprotein.
The aim of this study was to measure the anti-S antibody titres among the medical personnel who
had been fully vaccinated with different types of vaccines, and to compare them with those who were
COVID-19 convalescents.
Material and methods: In this study serum was collected from 261 healthcare workers, of whom
227 were vaccinated, while 34 were recovered participants who were not immunised. Serum samples
were collected 21 days after the first dose and 60 and 180 days after the second dose of the vaccines
and tested with a commercial ELISA kit.
Results: The highest antibody level (12 AU/ml) was measured in the Pfizer-BioNTech group,
followed by Sinopharm (9.3 AU/ml), Sputnik V (5.9 AU/ml), Sinovac (4.6 AU/ml) and Oxford/AstraZeneca vaccine (2.5 AU/ml) 60 days after the second dose of the vaccines (90 days after the first dose).
The seropositivity rate for mRNA vaccine was 88.5%, for vector vaccines 86.2% and for inactivated
vaccines 71.4%. When comparing these antibody levels with COVID-19 convalescents, higher antibody
titres were found in vaccinated participants (5.76 AU/ml vs 7.06 AU/ml), but the difference was not
significant (p = 0.08).
Conclusions: Individuals vaccinated with mRNA and vector vaccines had a higher seroconversion
rate compared to the group vaccinated with inactivated vaccines, or convalescents.