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How do we know if a vaccine is safe?

In this article, an overview of the steps of vaccine safety assessment is given. Pre-clinical assessment of vaccine safety is discussed in more depth.
Scientist pipetting into test tubes
© Pexels photo by ThisIsEngineering shared under a Creative Commons (BY) license
Safety testing is an integral component of vaccine development and use. New vaccines can only be licensed once sufficient evidence of safety is available.

Careful safety monitoring of newly licensed vaccines via surveillance is also essential post-licensure to ensure any concerning uncommon and rare side effects are identified. The image below shows the different phases of assessment vaccines go through before they are made available for public use.

Infographic showing the different stages a vaccine goes through to ensure it's safe. It starts with pre-clinical assessment, then clinical trials and post licensure assessment.

Image recreated based on Australian Academy of Science. This is available as a PDF.

Pre-clinical Assessment of Vaccine Safety:

Prior to clinical trials in humans, all new vaccines and medicines must undergo testing in the laboratory and in animal studies. No animal model can predict all potential side effects in humans and, for this reason, human studies are still needed to assess vaccine safety. However, if any concerning side effects are seen in animal studies, then regulatory approval to test a vaccine in humans may not be given.

In the next step we will look at the different phases of the clinical trials.

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Vaccine Development: Finding a Vaccine for COVID-19 and Future Pandemics

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