Work

From first infection to reinfection: Comparing Nucleocapsid antibody kinetics in vaccinated and unvaccinated adults

Year: 2025

Type: article

Abstract: Determining infection histories of individuals with prior immunity is critical to studying SARS-CoV-2 imprinting and vaccine responses. To better understand the response to infection, we examine nucleocapsid protein antibody dynamics around first and second SARS-CoV-2 infections in vaccinated and unvaccinated adults. The presence and levels of nucleocapsid-antibodies were measured around first and second SARS-CoV-2 infections. Antibody waning was measured with accelerated failure time models. After first-infections 95.8 % (88.5–98.6 %) of unvaccinated and 89.4 % (86.5–91.7 %) of vaccinated participants seroconverted. Vaccinated adults had 45.5 % shorter seropositivity (event time ratio = 0.55, 95 %CI: 0.45–0.66). After second-infections, 89.1 % (76.9–95.3 %) of vaccinated and 94.4 % (74.2–99.0 %) of unvaccinated participants had a 4-fold rise in antibody levels. Regardless of vaccination, antibody levels after second-infections are significantly higher than after first-infections. These findings suggest nucleocapsid serology can inform researchers about past infections regardless of exposure status, and potentially differentiate between initial infections and reinfections. • Spike serology has limited ability to detect infections in those with previous exposures. • Most participants seroconvert for Nucleocapsid antibodies after a first infection. • Vaccination is associated with shorter periods of nucleocapsid seropositivity following infection. • Nucleocapsid antibody levels rise significantly more after a second infection. • Nucleocapsid serology may help reconstruct infection histories in both vaccinated and unvaccinated adults.

Source: Vaccine

DOI: 10.1016/j.vaccine.2025.127593