How are new drugs and vaccines tested?

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1. Discovery research
2. Pre-clinical testing
3. Clinical testing
4. Regulatory review and approval
5. Manufacturing and delivery of the new product

Usually, new medicines and vaccines are developed through a series of steps. The steps are designed to make sure that the medicine or vaccine works and is safe.  

These are the 5 phases of new medicine or vaccine development:

1. Discovery research

Discovery research means that laboratory scientists look into ways to achieve the desired effect in the body at a molecular level. In the case of a vaccine, that means they are looking for ways to create an immune response to the virus without the person having to be exposed to the virus itself.

2. Pre-clinical testing

Pre-clinical testing is when the safety and effectiveness of the potential vaccine or drug is tested in animals. Pre-clinical studies take place before any testing in humans is done.

3. Clinical testing

After the previous two stages have been completed successfully, the potential vaccine or drug can be tested in humans. This step has three phases, and success at each stage does not guarantee success at the next stage.

• Phase I – testing to assess safety and effectiveness in a small number of healthy volunteers.
• Phase II – testing in a larger number of volunteers to get a better idea of how the vaccine or drug works in different groups of people and the best dose to use. From this stage onwards, a proportion of volunteers in the study will usually be given an inactive 'placebo'. The new product can be compared to this placebo to see it works any better.
• Phase III – wider testing to demonstrate the safety and effectiveness of the vaccine or drug in a much larger number of people, usually numbering in the thousands. These will often be people of different ages, ethnicities, and with different health conditions. In this stage, researchers hope to confirm the best way of giving the vaccine, including the size of dose and how many doses are needed. They are also looking to identify any side effects and clarify which groups of people the drug or vaccine is not suitable for.

4. Regulatory review and approval

Before the new drug or vaccine can be approved, the results of each phase and other information are submitted to regulators, who decide whether or not it is safe and effective enough to be used by the general public. In the UK, the main regulator is called the Medicines and Healthcare products Regulatory Agency (MHRA).  

5. Manufacturing and delivery of the new product

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