A vaccine doesn’t go from a laboratory to a hospital overnight. Before it reaches the public, it goes through years of research and several rounds of testing to answer two important questions: Is it safe? And does it work?
The journey begins with preclinical research. Scientists first study the vaccine in the laboratory and then in animals to understand how it behaves and whether it can safely trigger an immune response. If the results are promising, the developers submit an Investigational New Drug (IND) application to the regulatory authority, requesting permission to begin testing in people.
Human testing happens in three stages. Phase 1 involves a small group of healthy volunteers and focuses mainly on safety. Phase 2 includes a larger group to determine the right dose and continue monitoring safety while studying the immune response. Phase 3 involves thousands, and sometimes tens of thousands, of participants to confirm that the vaccine works and to identify less common side effects.
If these studies show that the benefits outweigh the risks, the manufacturer submits a Biologics License Application (BLA). Experts at the regulatory agency carefully review all the data collected over the years. Independent advisory panels, such as the Vaccines and Related Biological Products Advisory Committee (VRBPAC), may also examine the evidence and provide recommendations. At the same time, manufacturing facilities are inspected to ensure that every vaccine dose is produced to the same quality standards.
Even after a vaccine is licensed, scientists continue to monitor its safety through systems such as the Vaccine Adverse Event Reporting System (VAERS). This helps identify very rare side effects that may only become apparent after millions of doses have been been administered.
Every approved vaccine represents years of careful research, testing, and review. The process is designed to ensure that vaccines are both safe and effective before they become part of public health.
