Cohort Profile: A longitudinal Victorian COVID-19 cohort (COVID PROFILE)
Authors: Eriksson Emily M. , Hart Anne , Forde Maureen , Foroughi Siavash , Kiernan-Walker Nicholas , Mazhari Ramin , Lucas Erin C. , Margetts Mai , Farchione Anthony , Sheerin Dylan , Ashdown George , Evans Rachel , Chen Catherine , Ruybal-Pesántez Shazia , Conway Eamon , Barrios Marilou H. , Cornish Jasper , Edmonds Maria , Henneken Lee M. , Ioannidis Lisa J. , Olechnowicz Sam W. Z. , Munnings Ryan B. , Groom Joanna R. , Hansen Diana S. , Bowden Rory , Coussens Anna K. , Tye-Din Jason A. , Bryant Vanessa L. , Mueller Ivo 
Published: April 2023

AbstractPurposeThe COVID PROFILE cohort is a longitudinal clinical study based in Victoria Australia, which was established to understand immunity to SARS-CoV-2 in alow transmission population settingand to identify immunological markers of long-term immunity and immune-dysregulation after both infection and vaccination. Additionally, this cohort was established as a biobank resource for researchers to address other health-related immunological questions.ParticipantsWe enrolled 178 adult community members, including household contacts, who had either recovered from a SARS-CoV-2 infection or were SARS-CoV-2 naïve. Only participants ≥18 years of age and, in the case of female participants, non-pregnant women at the time of enrollment were included in the study. Detailed COVID-19 clinical data, vaccination status, medical history and demographics was collected.Findings to dateAt enrollment, we found that 87.8% of COVID-19 recovered individuals were seropositive with detectable levels of anti-SARS-CoV-2 IgG antibodies. Seronegative COVID-19 recovered individuals included asymptomatic individuals or participants that were enrolled more than 12 months after their COVID-19 diagnosis. Except for one individual who was seropositive at baseline despite a previous SARS-CoV-2 PCR negative diagnosis, all household contacts and other community members enrolled as SARS-CoV-2 PCR negative, were seronegative for all SARS-CoV-2-specific antibodies tested. The infection rate (re-infection or new infection) during 24 months of the study was 42.7%, as determined by either rapid antigen tests, PCRs or serology screens. Of the SARS-CoV-2 recovered participants, 32.6% reported ongoing symptoms at enrollment of which 47% had already experienced ongoing symptoms for more than 12 weeks.Future PlansCOVID PROFILE will be used to comprehensively understand temporal immunity to SARS-CoV-2 and COVID-19 vaccines and to understand the impact of host immunological composition on such immunity and symptom severity. Additionally, studies focusing on understanding immunity following breakthrough infections and immunological risk factors that contribute towards development of long COVID are planned.Limitations/Strengths of the studyExtensive clinical information is available and longitudinal samples (blood, saliva and oropharyngeal swabs) collected at regular intervals up to 2.5 years after initial enrolment.This low SARS-CoV-2 transmission population cohort, enables exploration of difference in both the acquisition and maintenance of naturally acquired and vaccine-induced immunity not confounded by prior, frequent and/or undetected exposures.Extensive biobank of numerous blood fractions and biospecimen enables further exploration of mucosal immunity, nasal microbiome and humoral and cellular immunity over time.The cohort may be limited in addressing research questions regarding outcomes and risk factors and their associations where low incidence is expected.