Although
mRNA vaccines against SARS-CoV-2 were highly efficacious against severe illness and hospitalization, they seem to be less effective in preventing
infection months after vaccination, especially with the Delta variant.
Breakthrough infections might be due to higher infectivity of the variants, relaxed protective measures by the general public in "
COVID-19 fatigue", and/or waning immunity post-vaccination. Determining the
neutralizing antibody levels in a longitudinal manner may address this issue, but technical complexity of classic assays precludes easy detection and quick answers. We developed a lateral flow immunoassay NeutraXpress™ (commercial name of the test kit by Antagen Diagnostics, Inc.) and tested fingertip blood samples of subjects receiving either Moderna or Pfizer
vaccines at various time points. With this device, we confirmed the reported clinical findings that
mRNA vaccine-induced
neutralizing antibodies quickly wane after 3-6 months. Thus, using rapid tests to monitor
neutralizing antibody status could help identify individuals at risk, prevent
breakthrough infections, and guide social behavior to curtail the spread of
COVID-19.