Introduction: The administration of a third vaccine is ongoing in many countries, but the evaluation of vaccine-induced immunity is still insufficient. This study evaluated anti-spike IgG levels in 373 health care workers six months after the BNT162b2 vaccination. Methods: Dynamics of anti-spike IgG levels six months after the 2nd vaccination were assessed in 49 participants (Analysis-1). A cross-sectional assessment of anti-spike IgG level was performed in 373 participants (Analysis-2). Participants positive for anti-nucleocapsid IgG or IgM and receiving immunosuppressants were excluded from Analysis-2. Results: In Analysis 1, the median anti-spike IgG level was lower in the older age group and decreased consistently after the second vaccination regardless of age. In Analysis-2, the anti-spike IgG level was significantly negatively associated with age (r = -0.35, p < 0.01). This correlation remained statistically significant (r = -0.28, p < 0.01) even after adjusting for sex, BMI, smoking habits, alcohol drinking habits, allergies, and the presence of fever or other adverse reactions at the time of the vaccination. Alcohol drinking habit was also associated with the anti-spike IgG level; daily alcohol drinkers had significantly lower anti-spike IgG levels than never alcohol drinkers. Sex, smoking habit, allergy, and fever and other side effects after the vaccination were not associated with anti-spike IgG levels six months after the 2nd vaccination. Conclusions: Six months after the vaccination, the anti-spike IgG level was substantially low among older persons and daily alcohol drinkers.
Dynamics of anti-Spike IgG antibody level after full BNT162b2 COVID-19 vaccination in health care workers