Ensuring COVID-19 vaccines are safe and effective takes time. Typically, vaccine development takes about 10 years.3 This is because vaccines must pass a series of pre-clinical studies (usually laboratory based), clinical trials in humans, and approval processes before they become available for use.
The steps of the clinical trial process are known as phases. Any vaccine in development must progress through each testing phase to make sure it is safe and effective.4
Usually the different phases can take months, years or even longer. But due to the urgency of finding a vaccine to prevent SARS-CoV-2 (the virus that causes COVID-19), this process is being fast-tracked.
What happens in each phase of a clinical trial?
Phase I clinical trials are done to test a medicine – in this case a vaccine – for the first time in a small group of people – usually a few dozen healthy volunteers.
A phase I trial works out if the vaccine is safe by evaluating how the human body reacts to the vaccine and observing for any side effects.
Phase II trials usually involve a few hundred people and provide information about how well the vaccine works (efficacy) as well as further information about the safest dose range.
Phase III trials usually involve a few thousand people, testing the efficacy and safety in a larger group.
Before a clinical trial can move to Phase IV, a government regulatory body examines the Phase III results and decides whether to approve the vaccine for use in the general population. In Australia, approval is given by the Therapeutic Goods Administration (TGA).
Phase IV clinical trials are conducted after the product has been approved and involve gathering information about efficacy and safety in the general population.5,6