<p>Rapid, sensitive, multiplexed antibody detection technologies are essential for assessing vaccine efficacy and recipient immunity against viruses. As severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants continue to emerge and novel viruses may pose potential threats in the near future, personalized vaccines can be precisely tailored to an individual’s measured immunity to help mitigate the symptoms of infection and viral spread. Here, we present giant magnetoresistive (GMR) biosensor microarrays for the quantitative multiplexed detection of antibodies against SARS-CoV-2 variants. The multiplexed GMR biosensor microarrays demonstrated high sensitivity, comparable to that of the single-plex enzyme-linked immunosorbent assay, enabling multiplexed measurements using blood obtained from finger pricks. Additionally, the GMR biosensor microarrays demonstrated compatibility with clinical samples and could detect variant-specific antibodies in serum, allowing for the assessment of current immunity status. Notably, an increased concentration of antibodies against the Omicron variant was clearly observed two weeks after receiving an Omicron-based booster vaccination. These results indicate that GMR biosensor microarrays offer a practical point-of-care tool for monitoring humoral immunity and guiding personalized vaccination schedules, thereby supporting immunity management against SARS-CoV-2 and future viral threats.</p>