Effect of COVID-19 on Anti-S Antibody Response in Healthcare Workers Six Months Post-Vaccination

The current study aimed to determine to what extent prior COVID-19 infection affects the response of specific antibodies following vaccination. The study involved 173 healthcare professionals who completed the two-dose vaccination course with BNT162b2, including 40 who previously experienced clinical COVID-19. The levels of anti-SARS-CoV-2 S1S2 IgG (anti-S) and, in some cases, anti-SARS-CoV-S-RBD IgG (anti-S-RBD) were determined six months after complete vaccination. A level exceeding the cut-off values for both anti-S and anti-S-RBD was observed in 100% of subjects, but after setting the analysis to 5- and 10-fold cut-off levels, the percentage of subjects meeting this criterion was significantly higher for anti-S-RBD. The 100-fold cut-off level was achieved by only 21% and 16% for anti-S and anti-S-RBD, respectively. Anti-S and anti-S-RBD levels above ten times the positive cut-off were respectively observed in 91% and 100% individuals with a history of COVID-19, while among those without COVID-19, these values were 64% and 90%, respectively. Significantly higher incidence of values above 10 and 100 times the cut-off became apparent among people with a history of COVID-19. In conclusion, vaccination against COVID-19 following infection with the disease provides higher levels of specific antibodies 6 months after vaccination than those of individuals without a history of the disease, which supports the use of a booster dose, particularly for those who have not experienced SARS-CoV-2 infection.