Development usually takes around five years. Once you pick a disease to target, you have to create the vaccine and test it on animals. Then you begin testing for safety and efficacy in humans.
Safety and efficacy are the two most important goals for every vaccine. Safety is exactly what it sounds like: is the vaccine safe to give to people? Some minor side effects (like a mild fever or injection site pain) can be acceptable, but you don’t want to inoculate people with something that makes them sick.
Efficacy measures how well the vaccine protects you from getting sick. Although you’d ideally want a vaccine to have 100 percent efficacy, many don’t. For example, this year’s flu vaccine is around 45 percent effective.
To test for safety and efficacy, every vaccine goes through three phases of trials:
- Phase one is the safety trial. A small group of healthy volunteers gets the vaccine candidate. You try out different dosages to create the strongest immune response at the lowest effective dose without serious side effects.
- Once you’ve settled on a formula, you move onto phase two, which tells you how well the vaccine works in the people who are intended to get it. This time, hundreds of people get the vaccine. This cohort should include people of different ages and health statuses.
- Then, in phase three, you give it to thousands of people. This is usually the longest phase, because it occurs in what’s called “natural disease conditions.” You introduce it to a large group of people who are likely already at the risk of infection by the target pathogen, and then wait and see if the vaccine reduces how many people get sick.
After the vaccine passes all three trial phases, you start building the factories to manufacture it, and it gets submitted to the WHO and various government agencies for approval.
For COVID-19, financing development is not an issue. Governments and other organizations (including our foundation and an amazing alliance called the Coalition for Epidemic Preparedness Innovations) have made it clear they will support whatever it takes to find a vaccine.
So, scientists are able to save time by doing several of the development steps at once. For example, the private sector, governments, and our foundation are going to start identifying facilities to manufacture different potential vaccines. If some of those facilities end up going unused, that’s okay. It’s a small price to pay for getting ahead on production.
Fortunately, compressing the trial timeline isn’t the only way to take a process that usually takes five years and get it done in 18 months.
Another way we’re going to do that is by testing lots of different approaches at the same time.
There are dozens of candidates in the pipeline.
As of April 9, there are 115 different COVID-19 vaccine candidates in the development pipeline.