Quantitative Evaluation of IgG Antibodies Against COVID-19 Vaccination

Researchers from the University of Antioquia in Medellin, Colombia, have published a new report on the COVID-19 pandemic, focusing on the measurement of antibody response to COVID-19 vaccination. The study notes that there is no standardized method to measure the antibody response to COVID-19 vaccination, and proposes that quantitative evaluation of antibodies against the virus could be a good correlate of protection. The study investigated the intensity of the immune response to COVID-19 vaccination in blood donor samples using a quantitative IgG antibody test against the receptor-binding domain (RBD) of the virus.

Key Takeaways:

• The study found that the median IgG antibody level was 1431 BAU/mL (Interquartile range: 680-3008) in 401 blood donors with a mean age of 37.7 years (Standard Deviation: 11.1).
• Donors who received the Moderna vaccine showed the best response, followed by those who received the Pfizer vaccine.
• Individuals with a history of COVID-19 had higher antibody levels than those without a history of the disease.
• Antibody levels remained above 1000 BAU/mL between 9 and 14 months after vaccination.

Statistics:

• 401 blood donors were included in the study.
• The median IgG antibody level was 1431 BAU/mL (IQR: 680-3008).
• Donors who received the Moderna vaccine showed the highest antibody response (mean: 1844 BAU/mL, SD: 1139.5).
• Donors who received the Pfizer vaccine showed a slightly lower antibody response (mean: 1638.5 BAU/mL, SD: 1056.8).
• Antibody levels remained above 1000 BAU/mL for 5-14 months after vaccination.

Sources:

• Intensity of IgG Antibody Response to Different Types of COVID-19 Vaccines in Blood Donors. Iatreia, 2025,38(4):594-606.
• Universidad de Antioquia (University of Antioquia)
• Medical Letter on the CDC & FDA, November 2, 2025; p 405.