Health Canada has approved three COVID-19 vaccines to date: Pfizer-BioNTech, Moderna, and most recently, Oxford-
With concerns over the highly transmissible COVID-10 variants observed in Canada, public health officials and drug manufacturers alike, are trying to estimate how effective current vaccines will be.
Understanding vaccine efficacy
Vaccines are reviewed for safety/efficacy during various phases of clinical trials and following market authorization. Even improvements in efficacy are reviewed by regulators if observed over time. Generally, the efficacy of a COVID-19 vaccine is the percent reduction in new cases observed during a clinical trial (treatment group vs placebo).
Vaccine effectiveness is how well a vaccine works in real-world conditions once people outside of a clinical trial have received it. Drug effectiveness data accumulates over time, through what regulators call ‘post-market surveillance’. Per Health Canada Regulations, manufacturers are required, by law, to constantly monitor and submit safety and effectiveness data to ensure the health and safety of Canadians following market authorization of drugs.
It’s worth noting that not all vaccines are 100% effective. In fact, very few are. The annual flu shot, for example, is 40-60% effective. There are various reasons why this is the case, for example the health and characteristics of the person being vaccinated (e.g., age, health risk factors, etc.) and changes in viruses as they naturally evolve and change.
So, which vaccine is the best one to take?
All COVID-19 vaccines authorized to date by Health Canada have proven safe and effective to take in accordance with the labelled indications. All three Health Canada approved COVID-19 vaccines have proven highly effective at preventing severe symptoms in the dominant COVID-19 strain.
When it comes to the new COVID-19 variants, such as the UK and South Africa variants, more data is needed. For current vaccines authorized by Health Canada, preliminary findings show AstraZeneca is 75% effective against the UK variant and 10% effective against the South Africa variant, while Moderna is over 90% effective against the UK variant.
Please consult a licensed physician when determining which vaccine is appropriate for you, based on your age and other relevant health risk factors.
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