Cohort profile: Stop the Spread Ottawa (SSO)—a community-based prospective cohort study on antibody responses, antibody neutralisation efficiency and cellular immunity to SARS-CoV-2 infection and vaccination

Since December 2019, the COVID-19 virus has infected over 300 million people and caused more than 5.4 million deaths worldwide. Global research efforts are ongoing to describe the strength and duration of immune response generated by natural infection and/or vaccination among different groups of people, including individuals with immunocompromising conditions and people with PASC (post-acute sequelae of COVID-19). Most persons recovering from COVID-19 develop antibodies between 1 – 2 weeks post-symptom onset. However, people with an immunocompromised state may not elicit a sufficient immune response to vaccination. PASC continues to be a major public health concern, and there is no consensus on etiology or biomarkers. Large prospective cohort studies are pivotal to the characterization of long-term immune responses among diverse populations.

We launched a 1000-person longitudinal study (Stop the Spread Ottawa, SSO) to describe the quality, severity, and duration of the COVID-19 immune response. Since October 2020, adults (≥18 years of age) who tested positive for COVID-19 (convalescents) or at high risk of exposure to the virus (under surveillance) have provided monthly blood and saliva samples over a 10-month period. Three hundred participants will continue to provide bimonthly blood samples for 24 months (i.e., for up to 34 months overall). We published this profile to describe the composition of our cohort and lay a foundation for future SSO studies.

SSO continues to yield rich research potential, given: 1) The collection of pre-vaccine baseline data and samples from the majority of participants; 2) Recruitment of diverse subgroups of interest, and 3) A high level of participant retention and compliance with monthly sampling. The 24-month study extension will maximize opportunities to track SARS-CoV-2 immunity and vaccine efficacy, detect and characterize emerging variants, and compare subgroup humoral and cellular response robustness and persistence: https://covarrnet.ca/investigating-long-term-variables-to-sars-cov-2-infection-and-vaccine-immunity/.

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