Since the first smallpox vaccine was created in 1796, scientists have made incredible progress in reducing and even eradicating serious diseases through vaccination. Vaccinations play a critical role in protecting public health, but before a vaccine can be widely distributed, it must go through a series of clinical vaccine trial phases. According to Johns Hopkins Vaccination Resource Center, the process starts with several years of pre-clinical trials that test vaccines on animal candidates before the vaccine is ever tested on a human subject. Once a vaccine appears promising, it moves into four phases of vaccine trials in humans. Each phase is designed to carefully test a vaccine’s efficacy and safety.
Phase I Clinical Trials
Phase I of the vaccine trial process’s primary goal is to assess the safety of a new vaccine, specifically in human populations. Researchers want to ensure there are no serious long-term or short-term side effects. This first phase involves a small group of people (around 20-100) who are healthy adults with no underlying conditions. Volunteers receive the vaccine in a controlled setting where they are closely monitored. After administering the vaccine during the Phase I trial, researchers watch for side effects in the short term, such as soreness at the injection site, muscle aches, or fever, and longer-term immune responses.
Phase II Clinical Trials
Once a vaccine makes it through several months of safety testing in Phase I, it moves to Phase II, where researchers determine the optimal dose of the vaccine and continue to assess safety, but this time in a more diverse group of volunteers. Whereas Phase I only tests a vaccine on a few dozen healthy volunteers, Phase II expands this group to 100-300 people who have characteristics that mirror the intended recipients of the vaccine. Additionally, researchers can include individuals who are part of different ethnicities and backgrounds, as there is a recognized need for representing diverse populations in clinical trials. This larger and more diverse volunteer group is injected with either the new vaccine or is part of a control group where either a placebo or standard treatment is administered. Researchers collect information on safety and the immune response generated by different doses of the vaccine. They look to identify the dose that balances safety and immune protection.
Phase III Clinical Trials
The clinical trial expands to thousands of people in Phase III to confirm the efficacy of the vaccine being tested. Researchers continue to test the vaccine on a diverse population of 1000+ people that represent the general public, including those of different ages, genders, and ethnic backgrounds. These large-scale studies are often randomized and double-blind, meaning neither the researchers nor the participants who are receiving the vaccine or who are receiving the placebo know which they are receiving. After an injection of either the vaccine or a placebo, researchers monitor volunteers for any short-term or long-term side effects and gather extensive data on how well the vaccine prevents the disease. Phase III testing will determine whether a vaccine will be effective at curbing the disease in question and whether it will be approved for public distribution.
Phase IV Clinical Trials
The FDA is responsible for approving (also known as “licensing”) vaccines for use on the market. FDA investigators examine and evaluate the vaccine manufacturing facility for compliance with regulations, as well as confirm that the safety and effectiveness of the vaccine have been demonstrated during Phase I through Phase III testing. However, even after FDA approval, the vaccine is still monitored for long-term safety and effectiveness during Phase IV. This phase includes tens of thousands of participants or more, depending on the need for data. Instead of volunteers, the participants in this phase of research are the general public who have received the vaccine as part of their immunization program. The goal of Phase IV testing is to ensure the vaccine remains safe and effective by monitoring the long-term performance in different populations over time. Although very rare, a licensed vaccine can be withdrawn from use if there are any safety concerns that arise.
Understanding Vaccine Trial Phases at Aim Trials
Understanding the multiple phases of vaccine trials is important because it highlights the rigorous process that ensures vaccines are safe and effective. Each phase builds on the knowledge and data gained from the previous one, providing a comprehensive evaluation before a vaccine reaches the public.
At Aim Trials, we are committed to conducting high-quality clinical trials that contribute to the development of safe and effective vaccines. By learning about the four trial phases, our patients can understand the careful consideration and extensive research that go into every vaccine that Aim Trials uses in our clinical trials.
If you or someone you know is interested in contributing to the advancement of global health efforts, Aim Trials is equipped to facilitate vaccine studies for your company. Aim Trials has successfully partnered on Phase 2 through Phase 4 trials for multiple vaccines, including RSV, influenza, COVID-19, meningococcal, and more.
As a multi-specialty site integrated within a private practice, Aim Trials has extensive experience conducting high-volume vaccine studies. For the RSVpreF trial, we achieved a 98% eCOA compliance rate. With our diverse database of patients, we are also equipped to recruit effectively across hard-to-reach demographics. Our team has exceptional retention and compliance rates.
Contact [email protected] to learn about our vaccine trial capabilities.