Serological responses to SARS-CoV-2 in vaccinated and unvaccinated individuals: A Canadian study

• 159 Canadian individuals infected with COVID between March and Sept 2020 were studied. • Anti-Spike protein antibody responses and comorbidities were correlated with disease severity. • Older patients were more likely to have a response than younger patients. • Female patients over 60 years had more antibody responses compared those under 60 years. • Vaccinated patients had a stronger IgG response against S protein and a weaker response against N protein compared to unvaccinated patients. COVID-19 severity has been correlated with older age, male sex, and the presence of comorbidities; it is hypothesized that SARS-CoV-2 antibody responses are also correlated.159 unvaccinated patients with SARS-CoV-2 infections were assessed for IgA, IgG, and IgM titers, which were compared with disease severity, age, sex, presence of comorbidities, and time since infection. Anti-S and anti-Nucleocapsid (N) IgG responses were compared between unvaccinated and vaccinated SARS-CoV-2 positive patients. Anti-S IgA and IgM were better indicators of disease severity than IgG. IgG responses were more likely for patients over 60 years old. Female patients over 60 were more likely to have an antibody response than female patients under 60. Vaccinated patients had a stronger IgG response against S protein than against N protein likely due to immune imprinting. Disease severity was correlated with anti-S antibody responses and comorbidities in unvaccinated patients.