CITF-funded findings from studies of diverse populations

Many CITF-funded studies focus on Canadian populations as diverse as people experiencing homelessness, incarcerated individuals, people admitted to emergency units, and 2SLGBTQQIA+ communities. Here, we summarize results from the five presentations given during the breakout session “Responding to diverse populations” at the CITF Scientific Meeting in Vancouver, March 8-10, 2023. The study teams presented findings to better understand the different risks faced by specific populations and identify some explanatory factors for their SARS-CoV-2 infections.

1. Presenter and CITF PI Dr. Nathan Lachowsky: SARS-CoV-2 seroprevalence among 2SLGBTQQIA+ populations in Canada: A community-based mail-home dried blood spot study

The objective of this study was to evaluate the impacts of COVID-19 on the health, wellness, stigma, and material security of 2SLGBTQQIA+Two-spirit, lesbian, gay, bisexual, transgender, queer, questioning, intersex, asexual, and additional sexual orientations and gender identities. people and to estimate SARS-CoV-2 seroprevalence in this population.

• Between April and September 2022, 0.8% of the 2SLGBTQQIA+ study participants were negative for SARS-Cov-2 antibodies, and 99.2% were positive for SARS-CoV-2 antibodies.
• Online survey results showed the overall health of the 2SLGBTQQIA+ cohort between April and September 2022 was somewhat worse (33.8% of respondents) or about the same (41.8%) as before the COVID-19 pandemic.
• Of those with COVID-19, 2.2% were hospitalized and 0.7% were in intensive care units.
• About 17.7% of participants reported that they had Long COVID. The top five self-reported symptoms of Long COVID included fatigue, brain fog, depression or anxiety, cough, and sleep disturbances.

2. Presenter Ms. Lucie Richard and CITF PI Dr. Stephen Hwang: Identifying SARS-CoV-2 re-infections using testing and repeated sero-monitoring among people experiencing homelessness (PEH) in Toronto, Canada

This study, named Ku-gaa-gii pimitizi-win, aimed to assess the number and rate of SARS-CoV-2 reinfections among people experiencing homelessness in Toronto. Participants self-reported PCR and rapid antigen test (RAT) data and were tested for SARS-CoV-2 antibodies.

• PCR (saliva) or RAT tests showed that among non-Indigenous participants, most people who got reinfected did so six months after their first SARS-CoV-2 infection.
• Serology (finger-prick blood) data also showed that more participants had reinfections six months after their first SARS-CoV-2 infection.
• Potential reinfections identified through serology was three times greater than reinfections identified through PCR/RAT tests, suggesting that SARS-CoV-2 reinfections may be undercounted.
• People experiencing homelessness in Toronto were more likely to be reinfected with SARS-CoV-2 than people who had housing.

3. Presenter and CITF PI Dr. Nadine Kronfli: Seroprevalence and risk factors for SARS-CoV-2 among incarcerated individuals and correctional workers in Quebec, Canada: A cross sectional study

This study determined the SARS-CoV-2 seroprevalence among incarcerated people and correctional workers in Quebec’s provincial prisons. It also aimed to identify modifiable prison-related variables associated with SARS-CoV-2 seropositivity.

• The overall seropositivity among people in prison was 22% and more than 30% of participants with a positive serological test result had been asymptomatic.
• The overall seropositivity among correctional workers was 17%.
• Among people in prison, factors associated with an increased likelihood of being SARS-CoV-2 antibody seropositive included spending most or all of the time incarcerated since March 2020, employment during incarceration, having meals with cellmates or in their sectorArea of a prison which is fully enclosed by doors or walls but isn’t a room, or being in prison after an outbreak.
• Workers who were employed as correctional officers (rather than in other positions) and who did not feel concerned about acquiring SARS-CoV-2 from others in prison, had an increased likelihood of being SARS-CoV-2 seropositive.

4. Presenter Dr. Rhonda Rosychuk and CITF PI Dr. Corinne Hohl: When treat and release fails: Characteristics and outcomes of COVID-19 patients who return to the emergency department after discharge: An observational study by the Canadian COVID-19 Emergency Department Rapid Response Network (CCEDRRN)

The objective of this study was to describe the characteristics and outcomes of patients with COVID-19 who had unscheduled emergency department visits related to the disease.

• From March 1, 2020 to March 31, 2022, younger patients (0-18 years old) had shorter return times to emergency departments after discharge than older adults (seniors 80+ years).
• Whether patients had gone to the emergency department once or multiple times, a high proportion (7.2%) returned within 72 hours during the first two pandemic years, incurring substantial resources.
• Individuals who were older, pregnant, had active cancer, kidney disease, an organ transplant or substance use history were at increased likelihood of returning to the emergency department after discharge.

5. Presenter Dr. Larisa Lotoski and CITF PI Dr. Megan Azad: Predictors of SARS-CoV-2 IgG antibody levels in adults and children following two COVID-19 vaccine doses: Results from the CHILD COVID-19 Add-on Study

This study evaluated the persistence of SARS-CoV-2 IgG antibodies and the predictors of antibody production following COVID-19 vaccination.

• Hybrid immunity (having previous SARS-CoV-2 infection and two COVID-19 vaccine doses) helped maintain SARS-CoV-2 anti-spike IgG antibody levels and slowed the decay rate, compared to vaccination alone.
• Children demonstrated higher anti-spike SARS-CoV-2 IgG production compared to adults, with the highest levels seen at three months after two vaccine doses.
• Adults who received two doses of mRNA vaccine (Moderna or Pfizer-BioNTech) had higher antibody levels than those who received the AstraZeneca vaccine.
• Among those who received mRNA COVID-19 vaccines, individuals who had a previous SARS-CoV-2 infection, or were children, had higher levels of SARS-CoV-2 anti-spike IgG.