How are vaccines made?

How are new vaccines developed?

New vaccines are usually developed over the course of about 10 years, in several different stages.

Step 1: Choosing a disease to target

The first step is determining which diseases will be targeted with a vaccine. Some diseases, such as HIV, are not easy to target with a vaccine because of how the pathogen interacts with our immune system. Other diseases that are extremely rare, or rarely cause serious illness, and are not likely to be targeted for vaccine development due to the time and cost required.

Step 2: Choosing the best platform to produce an immune response

When a disease has been identified, next comes the exploratory phase, which can last several years. During the exploratory phase, researchers in the lab examine the bacteria or virus genetic structure to understand how the pathogen attacks our cells and makes us sick, and figure out which parts of it are the best candidates to target for a vaccine to produce the strongest immune response, called antigens. They use this information to create an “imitation infection” that teaches our immune system how to fight the pathogen without causing illness.

These days, scientists are trying to explore new ways to create vaccines. This includes mRNA and vector-based vaccines, which give our bodies genetic information about the pathogen and use our cell’s own machinery to generate the antigens for our immune system to recognize. It can also include creating new platforms and additives for delivering a vaccine that can improve the immune response and reduce potential side effects.

Step 3: Testing a vaccine in the lab

Once a potential vaccine has been developed, it is tested in the pre-clinical stage. Scientists test the vaccine on cells in a dish, using mathematical models, and in animal models to see whether it activates the immune system in the way it’s intended. Often vaccines don’t make it past this stage because they don’t produce the desired immune response.

Step 4: Clinical trials in humans

Vaccines that seem promising get approved for clinical testing by the FDA, which happens in three phases over the course of several years. These tests are focused on ensuring that the vaccine is safe and that it produces an effective immune response in human patients that persists over time. It’s important that vaccines are tested in large and diverse groups of people to find out if there are any very unusual or rare side effects and to make sure that the vaccine is equally effective for all participants.

A vaccine that passes all of these stages may be approved for distribution by the FDA, which continues to monitor the production of the vaccine to ensure it’s safe and effective.

Watch part one: How do vaccines work?

Watch part two: What are the different types of vaccines?

Watch part four: How does the FDA approve vaccines?