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After several reports on European countries suspending the use of the AstraZeneca COVID-19 vaccine, many Canadians are wondering if it is safe to use.

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What you should know

  • Law – Manufacturers in the pharmaceutical industry are required by law to report Adverse Drug Reactions (ADRs) to regulatory agencies such as Health Canada. ADRs are harmful unexpected reactions that are proven to have been caused by a drug. Reports are collected and reviewed from a global perspective, which means that manufacturers and regulatory agencies are always monitoring drug safety from the widest lens possible. In industry, we call this “pharmacovigilance.”
  • Timeline – Expedited reporting timelines are required for more severe reactions, to ensure the health and safety of consumers is protected. This requirement applies 24/7 and persists for years, even after a company no longer wishes to market the product. Regulators use ‘signal detection’ to identify a potential safety issues that warrant further investigation. Signals are new or known adverse drug reactions caused by a drug that warrant further and prompt investigation.
  • Investigation – Whenever an ADR is reported, Health Care professionals are involved in the analysis of the data to determine if the drug product is responsible, or if someone experienced the issue for other reasons that are not associated with use of the drug, e.g., new symptom of disease or chronic underlying health issue.

So, is there any evidence that the AstraZeneca vaccine caused blood clots?


Per the European Medicines Agency (EMA), there is no indication that the AstraZeneca COVID-19 vaccine poses any increased risk of blood clots. The incidence of blood clots is no higher than what is normally seen in the general population.

The investigation into these incidents is part of the normal pharmacovigilance process for all pharmaceutical drug products.

Why aren’t there reports of side effects for other COVID-19 vaccines, such as Pfizer-BioNTech or Moderna?

Adverse Events (AEs) have been reported for all COVID-19 vaccines, and nearly every single pharmaceutical drug on the market.

AEs are different from ADRs, though both are considered “side effects”. With AEs, no causal link to a drug product is suspected. With ADRs, a causal link is suspected to possibly exist, pending further investigation.

The clinical trial process is designed to identify any risks associated with pharmaceuticals, prior to sale and marketing to the population at large. This includes identifying any known AEs/ ADRs and ensuring drug labels include appropriate indications and warnings for use.

Once a drug is authorized for sale, many more thousands of consumers begin taking it and any side effects or safety issues are monitored 24/7 by regulatory professionals and Health Authorities all over the world.

Did this happen because the regulatory approval process of COVID-19 vaccines was rushed?


Health Canada prioritized the review of COVID-19 vaccines and allowed ‘rolling-submissions’ so manufacturers could submit data as soon as it became available. The assessment of vaccine safety, efficacy and quality was not compromised. COVID-19 vaccines must comply with Health Canada Regulations to maintain market authorization in Canada.

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