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

Abstract

PurposeTo investigate the robustness and longevity of SARS-CoV-2 immune responses conferred by natural infection and vaccination among priority populations such as immunocompromised individuals and people with post-acute sequelae of COVID-19 in a prospective cohort study (Stop the Spread Ottawa—SSO) in adults living in the Ottawa region. In this paper, we describe the study design, ongoing data collection and baseline characteristics of participants.ParticipantsSince October 2020, participants 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. As of 2 November 2021, 1026 adults had completed the baseline survey and 976 had attended baseline bloodwork. 300 participants will continue to provide bimonthly blood samples for 24 additional months (ie, total follow-up of 34 months).Findings to dateThe median age of the baseline sample was 44 (IQR 23, range: 18–79) and just over two-thirds (n=688; 67.1%) were female. 255 participants (24.9%) had a history of COVID-19 infection confirmed by PCR and/or serology. Over 600 participants (60.0%) work in high-risk occupations (eg, healthcare, teaching and transportation). 108 participants (10.5%) reported immunocompromising conditions or treatments at baseline (eg, cancer, HIV, other immune deficiency, and/or use of immunosuppressants).Future plansSSO continues to yield rich research potential, given the collection of pre-vaccine baseline data and samples from the majority of participants, recruitment of diverse subgroups of interest, and a high level of participant retention and compliance with monthly sampling. The 24-month study extension will maximise opportunities to track SARS-CoV-2 immunity and vaccine efficacy, detect and characterise emerging variants, and compare subgroup humoral and cellular response robustness and persistence.

COVID-19 vaccine immunogenicity in people with HIV

“…The current multi-center prospective observational cohort study (CTN 328) of PWH recruited from sites in Montreal, Toronto, Ottawa, and Vancouver, with the plan to compare the COVID-19 immune response produced by vaccination, with that of HIV-negative controls, who had data collected at the same time points, in a parallel cohort study (Stop the Spread Ottawa-SSO) [ 13 ]. The CTN328 protocol was previously published [ 9 ], and later amended to accommodate 3rd and 4th doses/boosters.…”

“…A subset of immunocompetent SSO participants was used as HIV-negative controls and was included if they had undergone parallel blood collection in relation to vaccination time. A detailed description of this cohort was recently published [ 13 ].…”

“…IgG antibody titers [binding antibody units (BAU)/ml] were generated by a conversion model (4-parameter log-logistic curve based on measurements from the WHO International Standard) (NIBSC 20.136). Assay description was previously published [ 13 , 18 ] and it has been used in other Canadian studies [ 13 , 19 , 20 ], enabling future results comparison across cohorts.…”

SARS-CoV-2 Vaccine-Induced T-Cell Response after Three Doses in People Living with HIV on Antiretroviral Therapy Compared to Seronegative Controls (CTN 328 COVAXHIV Study)

“…Cryopreserved peripheral blood mononuclear cells (PBMCs) from PLWH were obtained via the multi-centre prospective observational cohort study (CTN328) with recruitment sites located at the McGill University Health Center (Montreal, QC, Canada), University Health Network (Toronto, ON, Canada), the Ottawa Hospital (Ottawa, ON, Canada), and the British Columbia Centre for Excellence in HIV/AIDS (Vancouver, BC, Canada). Specimens from age-matched seronegative individuals were obtained from the Stop the Spread Ottawa (SSO) cohort [ 12 ]. Details regarding participant recruitment and inclusion/exclusion criteria for these cohorts have been previously described [ 8 , 12 ] and are outlined in Materials S1 .…”

“…Specimens from age-matched seronegative individuals were obtained from the Stop the Spread Ottawa (SSO) cohort [ 12 ]. Details regarding participant recruitment and inclusion/exclusion criteria for these cohorts have been previously described [ 8 , 12 ] and are outlined in Materials S1 . For the current study, participants were excluded if they had received any blood product or immunoglobulin preparation within 1 month of vaccination or if they experienced a SARS-CoV-2 infection (according to nucleic acid-, antigen-, or serology-based tests) during follow-up.…”