ABSTRACT
Objectives: Beginning early in the pandemic, there was a worldwide effort to develop effective vaccines against the SARS-CoV-2 virus. Before and after the approval and implementation of vaccines, there were concerns about their need as well as their safety and rapid development. We explored child demographic characteristics and parental concerns to identify factors associated with the decision to vaccinate. Methods: A cohort of 1035 children from Calgary was assembled in 2020 to participate in 5 visits every 6 months for survey completion and blood sampling for SARS-CoV-2 antibodies. Visits 1 to 2 occurred before approval of vaccines for children; Visits 3 to 5 occurred after vaccine approval for different age groups. We described vaccine concerns and utilized logistic regression to examine factors associated with the decision to vaccinate in children ≥5 years of age. Results: Children ≥12 years of age, of non-white or non-black ethnicity, and who had received previous influenza vaccines had higher odds of being vaccinated against SARS-CoV-2. Children with previous SARS-CoV-2 infection had lower odds of being vaccinated. The most common concerns in early 2021 were about vaccine safety. By summer 2022, the most common concern was a belief that vaccines were not necessary. Through the study 88% of children were vaccinated. Conclusions: Age, ethnicity, previous infections, and vaccine attitudes were associated with parental decision to vaccinate against SARS-CoV-2. For children who remained unvaccinated, parents continued to have safety concerns and questioned the necessity of the vaccine. Complacency about the need for vaccination may be more challenging to address and overcome than concerns about safety alone.
ABSTRACT
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.
