Vaccine Testing and Approval Process: Most vaccines have been in use for decades, with millions of people receiving them safely every year. Like medicines, every vaccine goes through extensive and rigorous testing to ensure it is safe before it can be introduced in a country’s vaccine programme. Each vaccine under development is evaluated to determine which antigen should be used to evoke an immune response. The preclinical phase is carried out without testing on humans. An experimental vaccine is first tested on animals to evaluate its safety and potential to prevent disease.

If the vaccine triggers an immune response, it is then tested in human clinical trials in three phases.

Phase 1

The vaccine is given to a small variety of volunteers to assess its safety, ensuring that it generates an immune response, and proper dose is decided. During this phase the vaccines are usually tested on young and healthy adult volunteers.

Phase 2

The vaccine is then given to hundreds of volunteers to further assess its safety and ability to generate an immune response. Participants in this phase have an equivalent characteristic as the people for whom the vaccine is meant. Multiple trials are usually conducted during this phase to evaluate different age groups and different formulations of the vaccine. The group of people that did not get the vaccine is usually included in this phase as a comparator group to determine whether the changes in the vaccinated group are attributed to the vaccine or have happened without any cause.

Phase 3

The vaccine is then given to thousands of volunteers and compared with a similar group of people who didn’t get the vaccine but received a comparator product. This is done to determine if the vaccine is effective against the disease it is designed to protect against and to study its safety in a much larger group of people. Most of the time, Phase 3 trials are conducted across multiple countries and multiple sites within a country to assure that the findings of the vaccine performance apply to many different populations.

During Phase 2 and Phase 3 trials, the volunteers and the scientists conducting the study are not informed whether the volunteers had received the vaccine being tested or the comparator product. This is known as “blinding” and is necessary to assure that neither the volunteers nor the scientists are influenced in their assessment of safety or effectiveness by knowing who group had received which product. Once the trial is over and all the results are finalized, the volunteers and also the trial scientists are informed if they had received the vaccine or the comparator.