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A 2026 decision from the Ontario Superior Court of Justice reinforces a fundamental principle of Canadian product liability law: an association between a product and an adverse medical condition does not establish causation. In Listovets v. AstraZeneca Canada Inc., the Court dismissed a negligence claim against a pharmaceutical manufacturer on summary judgment, holding that the plaintiff failed to prove that the medication in question was capable of causing the alleged harm.1
Case Overview
The plaintiff, Vladislav Listovets (“Listovets”), alleged that his diagnosis of Eosinophilic Granulomatosis with Polyangiitis (“EGPA”), was caused by a Symbicort Turbuhaler (“Symbicort”), an inhaled medication manufactured by the defendant, AstraZeneca Canada Inc. (“AstraZeneca”).
Listovets was prescribed Symbicort in 2004. After being diagnosed with EGPA in 2016, Listovets discovered that AstraZeneca had recently started warning Symbicort users about a potential association with EGPA.
Listovets commenced a negligence claim seeking $2.7 million in damages, asserting that AstraZeneca failed to warn consumers about the risk of EGPA from Symbicort use, and that AstraZeneca knew about this risk in 2002 but covered it up until 2015.2
AstraZeneca brought a motion for summary judgment limited to the issue of general causation.3 The Court characterized the motion as raising a “single issue”, namely whether Symbicort “can cause the development of EGPA in its ordinary use”.4 After reviewing the evidentiary record, the Court concluded that Listovets had failed to prove general causation, and the action was dismissed in its entirety.5
The Key Legal Principle
The Court began by reaffirming the essential elements of negligence:
- the defendant owes the plaintiff a duty of care;
- the defendant’s behaviour breached the standard of care;
- the plaintiff suffered compensable damages;
- the damages were caused in fact by the defendant’s breach; and
- the damages are not too remote in law.6
In the context of product liability and failure-to-warn claims, manufacturers have a legal obligation to inform consumers about risks that are built into a product’s use when those risks are known to them or should reasonably be known.7 However, before assessing breach of that duty, courts must determine whether the product is capable of causing the alleged harm in its ordinary use.8
The onus rests squarely on the plaintiff to establish general causation on a balance of probabilities.9 The Court further noted that, outside of the clearest cases, expert evidence is typically required to establish causation and breach in complex medical or scientific disputes.10
Why the Claim Failed
The central issue before the Court was whether Symbicort was capable of causing EGPA.
AstraZeneca relied on the expert evidence of a qualified respirologist, Dr. Nair, who opined that although there is an association between Symbicort and EGPA, “there’s no causal connection”.11 Dr. Nair explained the association likely reflects that inhaled corticosteroids treat asthma, often an early sign of EGPA, and that tapering oral corticosteroids can “unmask” underlying symptoms.12 Dr. Nair stated that there was no “biological explanation” for the drug to cause EGPA.13
Listovets filed no expert evidence, relying instead on regulatory warnings, adverse event reports, academic excerpts, and personal experience. The Court rejected each of these arguments. The 2015 product monograph noted parties “may present” with EGPA features but expressly stated that a “…causal relationship… has not been established,” which did not imply causation.14 Adverse event reports only showed an association, not causation. The academic articles were also inadmissible due to the lack of expert qualification, incompleteness or translation issues, and the inability to cross-examine the authors.15 Personal experience could not establish general causation, particularly given Dr. Nair’s evidence on biological implausibility.16
Final Decision
Inferring causation solely from association would effectively collapse the distinction between negligence and strict liability, an approach not recognized under Canadian law. The Court accepted Dr. Nair’s evidence and found that, while an association exists between use of Symbicort and EGPA, there was no causal connection.17
Practical Takeaways
This decision offers several practical lessons:
- General causation is a threshold requirement. Where a plaintiff cannot establish that a product is capable of causing the alleged harm, the claim may fail at an early stage.
- Expert evidence is critical. Complex scientific and medical issues require properly qualified opinion evidence, and the absence of such evidence may be fatal to a claim.
- Regulatory warnings do not necessarily concede causation. Product monograph updates referencing associations, particularly where they expressly state causation has not been established, do not amount to admissions of liability.
- Adverse event reporting does not equal proof of defect. Reports of adverse occurrences may trigger regulatory obligations but are not, in themselves, evidence of causation.
Key Takeaway
An association alone does not establish causation. In product liability law, plaintiffs must prove, on admissible evidence, that a product is capable of causing the alleged harm. Without proof of general causation, a failure-to-warn claim cannot succeed.
As of March 2026, there has been no appellate or judicial treatment of this decision. McMillan will continue to monitor for any further commentary or clarification from other courts regarding the application of these principles.
Footnotes
1. Listovets v AstraZeneca, 2026 ONSC 220 at para 56.
2. Ibid at para 13.
3. Ibid at para 16.
4. Ibid at para 29.
6. Ibid at para 30; citing Mustapha v Culligan of Canada Ltd, 2008 SCC 27, at para 3.
7. Listovets v AstraZeneca at para 31.
8. Ibid at para 32.
9. Ibid at para 33.
10. Ibid.
11. Ibid at para 34.
13. Ibid at para 37.
15. Ibid at para 43.
16. Ibid at para 45.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.
The foregoing provides only an overview and does not constitute legal advice. Readers are cautioned against making any decisions based on this material alone. Rather, specific legal advice should be obtained.
© McMillan LLP 2025
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