The Road to a New Vaccine

Vaccines are among the most effective tools we have for preventing viral infections. They're also an important part of reducing worldwide health and wealth inequities.

The World Health Organization (WHO) estimates that vaccines save millions of lives each year. And estimated cost savings are in the trillions. But vaccination has changed our world so much that it’s impossible to calculate its impacts. To people living today, a world without vaccines would be unrecognizable.

Because vaccines are given to healthy people on a large scale, often children, it’s very important to make sure they’re safe and they work. As with any medication, vaccines have risks. Most side effects are mild, but very rarely they can be more serious. That’s why government bodies like the FDA oversee every step of the vaccine development process.

There are lots of approaches for developing vaccines. To learn more, visit Types of Vaccines.

It’s very rare for people to be harmed by a vaccine. If you have questions, talk to a medical professional such as your doctor. They can help you understand the possible side effects of a specific vaccine. They can also advise you on what to do if you think a vaccine has made you or a loved one sick. To learn more about common and rare vaccine side effects, visit FAQs About Immunity & Vaccines.

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For more details about how vaccines are developed, visit Vaccine Development in Depth.

Clinical trials rely on volunteers! Vaccines need to be tested on people of all ages, genders, ethnicities, and lifestyles that the virus impacts. If you belong to a group or community that is heavily impacted, please consider signing up for a clinical trial. To find one in your area, visit

A Good Vaccine Is:

  • Safe. Because vaccines are given to huge numbers of healthy people, they must be very safe. It’s impossible to eliminate all risks associated with vaccines. But the risk of serious side effects, such as a strong allergic reaction, needs to be very low.
  • Effective. Vaccines must be proven to work. No vaccine can work 100% of the time—just as having an actual infection does not guarantee future immunity. But most vaccines are 90+% effective. That’s usually enough to protect a community where most people are vaccinated.
  • Scalable. So that everyone who needs a vaccine can get one, vaccines need to be made in huge amounts. Especially if it takes multiple doses to be protected, it may be necessary to make doses by the hundreds of millions or even billions. That means the manufacturing methods used to make the vaccine need to work on a large scale. This is sort of like how factories that make food use different tools and methods than the ones you use at home.
  • Cost effective. Vaccination costs much less than treating a person who gets sick from the infection the vaccine is designed to prevent. And they should be available to everyone who needs them, regardless of their ability to pay. But if a vaccine is expensive to make, this goal is harder to meet. That’s why it’s important to consider cost early in the vaccine development process.

Who Makes Sure All These Goals Are Met?

Any new vaccines need to go through a rigorous testing process that’s overseen by a government agency. In the US, all vaccines are licensed through a division of the Food and Drug Administration (FDA), called the Center for Biologics Evaluation. Other countries have similar agencies, and they follow a common set of guidelines. The WHO coordinates vaccine development efforts around the world. These agencies make sure vaccine developers follow proper procedures and minimize risks. They oversee everything from how experiments are designed to how vaccines are made and labeled. Before testing can even begin in people, the agency looks at data from earlier research. They approve testing in people only when there is enough promising evidence to suggest that the vaccine should be safe and effective. And they approve a vaccine for general use only after clinical trials show good results.

Who are the actual people involved in vaccine oversight? The FDA has employees who specialize in all aspects of vaccine development and stay up to date on the latest research. Non-FDA employees are also part of the vaccine approval process. Safety and efficacy data are reviewed by an independent panel of expert scientists, physicians, biostatisticians, and consumer representatives.

How Long Does Vaccine Approval Take?

Just like the illnesses they're designed to prevent, every vaccine is different. Any new vaccine has to be designed from scratch, and it needs to go through a rigorous testing process.

On average, developing a new vaccine takes a little more than 10 years. But there’s a lot of variability. Before 2020, the fastest vaccine developed was for mumps. It took 4 years, and it was approved in 1967. On the other extreme is HIV. The search for a vaccine began in the early 1980s, and nothing has yet been approved.

In an outbreak situation, where a virus is sweeping through a vulnerable population, approval can be fast-tracked. For example, in 2019 a viral vector vaccine was approved for Ebola after just 5 years. It may not seem that way, but that was very fast—especially considering the vaccine was the first of its kind approved for human use. With the novel coronavirus SARS-CoV-2, vaccine development efforts are poised to smash all previous records.

No matter how long it takes to get approved, any new vaccine has to go through all the steps in the process. Even when a vaccine is “fast-tracked,” it still has to meet all the safety rules and go through multiple rounds of testing.


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