LAUSR

Developing reliable, rapid, and quantitative point‐of‐care testing (POCT) technology of SARS‐CoV‐2‐specific antibodies and understanding longitudinal vaccination response kinetics are highly required to restrain the ongoing coronavirus disease 2019 (COVID‐19) pandemic. We demonstrate a novel portable, sensitive, and rapid chemiluminescent lab‐on‐fiber detection platform for detection of anti‐SARS‐CoV‐2 antibodies: the chemiluminescent lab‐on‐fiber immunosensor (c‐LOFI). Using SARS‐CoV‐2 Spike S1 RBD protein functionalized fiber bio‐probe, the c‐LOFI can detect anti‐SARS‐CoV‐2 immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies with high sensitivity based on their respective horseradish peroxidase‐labeled secondary antibodies. The limits of detection of anti‐SARS‐CoV‐2 IgG and IgM antibodies were 0.6 and 0.3 ng/ml, respectively. The c‐LOFI was successfully applied for direct detection of anti‐SARS‐CoV‐2 antibodies in whole blood samples with simple dilution, which can serve as a finger prick test to rapidly detect antibodies. Furthermore, the longitudinal immune response (>12 months) kinetics following three‐dose inactivated virus vaccines was evaluated based on anti‐SARS‐CoV‐2 IgG detection results, which can provide important significance for understanding the immune mechanism against COVID‐19 and identify individuals who may benefit from the vaccination and booster vaccination. The c‐LOFI has great potential to become a sensitive, low‐cost, rapid, high‐frequency POCT tool for the detection of both SARS‐CoV‐2‐specific antibodies and other biomarkers.