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Statement by ICES on vaccine effectiveness preprint


ICES is aware of the controversy surrounding a preprint on vaccine effectiveness published on January 1st, 2022. An experienced group of researchers led the study. As stated in the preprint, their results may underestimate vaccine effectiveness against the SARS-CoV-2 Omicron variant due to the preliminary nature of the data used. An updated analysis is underway that will include more recent and more complete data on vaccine effectiveness against Omicron infection and hospitalization in Ontario. The research team will update the current preprint next week.

Scientists at ICES have worked diligently to make early research findings available to enable an evidence-informed health-system response to a rapidly evolving pandemic, ever mindful of the need to help keep Ontarians informed and safe. The pandemic has shifted the speed at which analyses and outcomes are made available due to the increased need for timely and responsive data. Scientists and research institutes are navigating the complexities of sharing early findings while ensuring the accuracy of results based on preliminary data. We endeavour to make the most up-to-date analyses available; however, decisions regarding preprint publication of studies (ones made publicly available before traditional peer-review) are made on a study-by-study basis. As a result, preprint outcomes can change as more data are received and the analyses continue. Our research team works to provide updated results to ensure transparency and accuracy. ICES is continually working to strengthen these processes.

ICES is an independent, non-profit research institute that uses population-based health information to produce knowledge on a broad range of healthcare issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting healthcare needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad, and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy. In October 2018, the institute formerly known as the Institute for Clinical Evaluative Sciences formally adopted the initialism ICES as its official name. For the latest ICES news, follow us on Twitter: @ICESOntario

Media Contact

Niveen Saleh
Director of Communications
[email protected]


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