A longitudinal seroepidemiology study to evaluate antibody response to SARS-CoV-2 virus infection and vaccination in children in Calgary, Canada from July 2020 to April 2022: Alberta COVID-19 Childhood Cohort (AB3C) Study.

BACKGROUND: Measurement of SARS-CoV-2 antibody seropositivity is important to accurately understand exposure to infection and/or vaccination in specific populations. This study aimed to estimate the serologic response to SARS-CoV-2 virus infection and vaccination in children in Calgary, Alberta over a two-year period. METHODS: Children with or without prior SARS-CoV-2 infections, were enrolled in Calgary, Canada in 2020. Venous blood was sampled 4 times from July 2020 to April 2022 for SARS-CoV-2 nucleocapsid and spike antibodies. Demographic and clinical information was obtained including SARS-CoV-2 testing results and vaccination records. RESULTS: 1035 children were enrolled and 88.9% completed all 4 visits; median age 9 years (IQR: 5,13); 519 (50.1%) female; and 815 (78.7%) Caucasian. Before enrolment, 118 (11.4%) had confirmed or probable SARS-CoV-2. By April 2022, 39.5% of previously uninfected participants had a SARS-CoV-2 infection. Nucleocapsid antibody seropositivity declined to 16.4% of all infected children after more than 200 days post diagnosis. Spike antibodies remained elevated in 93.6% of unvaccinated infected children after more than 200 days post diagnosis. By April 2022, 408 (95.6%) children 12 years and older had received 2 or more vaccine doses, and 241 (61.6%) 5 to 11 year-old children had received 2 vaccine doses. At that time, all 685 vaccinated children had spike antibodies, compared with 94/176 (53.4%) of unvaccinated children. CONCLUSIONS: In our population, after the first peak of Omicron variant infections and introduction of COVID-19 vaccines for children, all vaccinated children, but just over one-half of unvaccinated children, had SARS-CoV-2 spike antibodies indicating infection and/or vaccination, highlighting the benefit of vaccination. It is not yet known whether a high proportion of seropositivity at the present time predicts sustained population-level protection against future SARS-CoV-2 transmission, infection or severe COVID-19 outcomes in children.

Challenges and recommendations for COVID-19 public health messaging: a Canada-wide qualitative study using virtual focus groups.

OBJECTIVES: To understand Canadian's attitudes and current behaviours towards COVID-19 public health measures (PHM), vaccination and current public health messaging, to provide recommendations for a public health intervention. DESIGN: Ten focus groups were conducted with 2-7 participants/group in December 2020. Focus groups were transcribed verbatim and analysed using content and inductive thematic analysis. The capability opportunity motivation behaviour Model was used as our conceptual framework. SETTING: Focus groups were conducted virtually across Canada. PARTICIPANTS: Participants were recruited from a pool of individuals who previously completed a Canada-wide survey conducted by our research team. MAIN OUTCOME MEASURE: Key barriers and facilitators towards COVID-19 PHM and vaccination, and recommendations for public health messaging. RESULTS: Several themes were identified (1) participants' desire to protect family and friends was the main facilitator for adhering to PHM, while the main barrier was inconsistent PHM messaging and (2) participants were optimistic that the vaccine offers a return to normal, however, worries of vaccine efficacy and effectiveness were the main concerns. Participants felt that current public health messaging is inconsistent, lacks transparency and suggested that messaging should include scientific data presented by a trustworthy source. CONCLUSIONS: We suggest six public health messaging recommendations to increase adherence to PHM and vaccination (1) use an unbiased scientist as a spokesperson, (2) openly address any unknowns, (3) more is better when sharing data, (4) use personalised stories to reinforce PHM and vaccinations, (5) humanise the message by calling out contradictions and (6) focus on the data and keep politics out.