COVID-19 Antibodies in Vaccinated Healthcare Workers: The Security Currency

Background The coronavirus disease 2019 (COVID-19) vaccinations have brought new hope to the world and have a significant psychosocial impact on communities as well as healthcare systems around the globe. This study aimed to assess the antibody titer level among healthcare workers after at least six weeks of the second dose of the COVID-19 vaccine. Methods Participants of the study were healthcare workers of a tertiary care cardiac center including doctors, nursing staff, paramedics, and office staff. All participants were fully vaccinated with recommended double dose of available vaccine at least six weeks before the study. A blood sample of five milliliters was collected from all the participants by a trained phlebotomist at a local laboratory, and COVID-19 antibodies titer level was assessed using Food and Drug Administration (FDA) approved kit with a standard range of 1.0. This qualitative assay detects IgG and IgM as total antibodies targeted against nucleocapsid antigen performed on a fully automated cobas® 6000 analyzer (F. Hoffmann-La Roche Ltd, Basel, Switzerland) using electrochemiluminescence technology. COVID-19 antibodies titer levels were categorized as ≤100, 101-250, and >250. Results A total of 151 healthcare workers were included, of which 70.2% (106) were male. The history of COVID-19 infection before vaccination was found in 41.1% (62). The mean duration since the last dose of the vaccine was 89.6±40.07 days. In total 71.5% (108) had antibodies titer level of >250, which were mostly found in participants of younger age and who had previous COVID-19 infection. However, antibodies titer level of >250 were observed in 84% (21/25) at 61 to 90 days of vaccination, which declined to 80% (20/25) after 91 to 120 days and to 57.1% (32/56) after >120 days of vaccination. Conclusions Good antibodies titer levels were observed in vaccinated healthcare workers, especially in those who were younger and had previous COVID-19 infection.