This is a summary, written by members of the CITF Secretariat, of:

Collins E, Galipeau Y, Arnold C, Bhéreur A, Booth R, Buchan CA, Cooper C,  Crawley AM, Mccluskie P, McGuinty M, Pelchat M, Rocheleau L, Saginur R, Gravel C, Hawken S, Langlois MA, Little J. Clinical and serological predictors of Post COVID-19 Condition: Findings from a Canadian prospective cohort study. medRxiv 2023.07.29.23293334; doi:

The results and/or conclusions contained in the research do not necessarily reflect the views of all CITF members.

A CITF-funded study, published in preprint and not yet peer-reviewed, found positive associations between Post COVID-19 Condition (PCC), also known as Long COVID, and anti-spike (S), and anti-receptor binding domain (RBD) IgG titres, which were not statistically significant. It also found no association with infection-acquired anti-nucleocapsid (N) IgG concentrations. However, individuals with PCC had significantly higher neutralization efficiency, especially those who reported a deterioration in quality of life. The study was led by Dr. Marc-André Langlois in collaboration with Ms. Erin Collins and Dr. Julian Little (all from University of Ottawa).

Key findings:

  • Similar proportions of individuals with PCC (66.7%) and controls who had had COVID-19 in the past with no persistent symptoms ≥12 weeks post-infection (71.3%) tested positive for infection-acquired antibodies (anti-N). More individuals (94.1%) with PCC tested positive for anti-S (suggesting vaccine-induced or infection-acquired antibodies) and anti-RBD (95.1%) IgG, compared with controls (anti-S: 89.3%; anti-RBD: 84.4%). Similar differences were observed among the non-vaccinated subgroup.
  • More individuals with PCC were efficient SARS-CoV-2 neutralizers (showing neutralization of ≥85% of SARS-CoV-2 spike protein) than controls. In both unvaccinated and vaccinated subgroups, median neutralization efficiency was somewhat higher among individuals with PCC than controls.
  • Individuals with PCC who reported deterioration in quality of life due to persistent symptoms had higher IgG titres and median neutralization efficiency. They also had a higher proportion of efficient neutralizers than those with PCC who did not report poorer quality of life.
  • Those with PCC were more likely to have pre-existing allergies compared to controls.
  • Individuals with PCC, especially those who reported deterioration in quality of life, were more likely than controls to seek medical help for COVID-19 symptoms and describe complex and enduring health needs long after initial infection.

The study, part of a prospective study of over 1000 people followed-up at multiple time points for more than two years (Stop the Spread Ottawa / SSO), compared clinical and serological predictors among COVID-19 survivors with (n=102 cases) and without (n=122 controls) persistent symptoms ≥12 weeks post-infection. Participants ranged in age from 21-75 years old. Four primary serological predictors –- anti-N, anti-S, and anti-RBD IgG titres, and neutralization efficiency — were assessed, controlling for pre-determined clinical covariates.