Impact of recruitment strategies on individual participation practices in the Canadian National Vaccine Safety Network: prospective cohort study.

Background: The Canadian National Vaccine Safety (CANVAS) network conducted a multi-center, prospective vaccine safety study to collect safety data after dose 1 and 2 of COVID-19 vaccines and follow up safety information 7 months after dose 1.
Objective: This study aimed to describe and evaluate the recruitment methods used by CANVAS and the retention of participants by each modality.
Methods: CANVAS deployed a multi-pronged recruitment approach to reach a larger sample, without in-person recruitment. Three primary recruitment strategies were used: passive recruitment, technology-assisted electronic invitation through the vaccine booking system (auto-invitation), or auto-registration through the vaccine registries (auto-enrollment).
Results: Between December 2020 and April 2022, approximately 1.3 million vaccinated adults either self-enrolled or were auto-enrolled in CANVAS, representing about 5% of the vaccinated adult Canadian population. Approximately 1 million participants were auto-enrolled, 300,000 were recruited by auto-invitation, and 5,000 via passive recruitment. Overall survey completion rates for dose 1, dose 2 and the 7-month follow-up surveys were 51.7% (681,198 of 1,318,838), 54.3% (369,552 of 681,198), and 66.4% (452,076 of 681,198), respectively. Completion rates were lower among auto-enrolled participants compared to passively recruited or auto-invited participants who self-enrolled. However, auto-enrolled samples were much larger, which offset the lower completion rates.
Conclusion: Our data suggest that auto-enrollment provided an opportunity to reach and retain a larger number of individuals in the study compared to other recruitment modalities.
Competing Interests: MS has been an investigator on projects funded by GlaxoSmithKline, Merck, Moderna, Pfizer, and Sanofi-Pasteur outside the submitted work. All funds have been paid to his institute, and he has not received any personal payments. LV reports grants from Pfizer outside the submitted work. KT reports grants from the Coalition of Epidemic Preparedness Innovations for COVID-19 vaccine studies. JI has been an investigator on projects funded by GlaxoSmithKline and Sanofi-Pasteur outside the submitted work. All funds have been paid to her institute, and she has not received any personal payment. AM reports grants to her institution from Pfizer and Sanofi-Pasteur, and personal payments for consulting from AstraZeneca, Merck, GlaxoSmithKline, Moderna, Novavax, Pfizer, and Seqirus. JK has been an investigator on projects funded by GlaxoSmithKline, Merck, Moderna, and Pfizer, all outside the submitted work. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
(Copyright © 2024 Soe, Sadarangani, Naus, Muller, Vanderkooi, Kellner, Top, Wong, Isenor, Marty, De Serres, Valiquette, McGeer and Bettinger.)