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The Vaccine Testing Process
The development cycle of a vaccine, from lab to clinic.
PRECLINICAL TESTING: Scientists test a new vaccine on cells and then give it to animals such as mice or monkeys to see if it produces an immune response. We have confirmed 92 preclinical vaccines in active development.
PHASE 1 SAFETY TRIALS: Scientists give the vaccine to a small number of people to test safety and dosage as well as to confirm that it stimulates the immune system.
PHASE 2 EXPANDED TRIALS: Scientists give the vaccine to hundreds of people split into groups, such as children and the elderly, to see if the vaccine acts differently in them. These trials further test the vaccine’s safety and ability to stimulate the immune system.
PHASE 3 EFFICACY TRIALS: Scientists give the vaccine to thousands of people and wait to see how many become infected, compared with volunteers who received a placebo. These trials can determine if the vaccine protects against the coronavirus. In June, the F.D.A. said that a coronavirus vaccine would have to protect at least 50% of vaccinated people to be considered effective. In addition, Phase 3 trials are large enough to reveal evidence of relatively rare side effects that might be missed in earlier studies.
EARLY OR LIMITED APPROVAL: China and Russia have approved vaccines without waiting for the results of Phase 3 trials. Experts say the rushed process has serious risks.
APPROVAL: Regulators in each country review the trial results and decide whether to approve the vaccine or not. During a pandemic, a vaccine may receive emergency use authorization before getting formal approval. Once a vaccine is licensed, researchers continue to monitor people who receive it to make sure it’s safe and effective.
COMBINED PHASES: One way to accelerate vaccine development is to combine phases. Some coronavirus vaccines are now in Phase 1/2 trials, for example, in which they are tested for the first time on hundreds of people. (Note that our tracker would count a combined Phase 1/2 trial as both Phase 1 and Phase 2.)
The development cycle of a vaccine, from lab to clinic.
PRECLINICAL TESTING: Scientists test a new vaccine on cells and then give it to animals such as mice or monkeys to see if it produces an immune response. We have confirmed 92 preclinical vaccines in active development.
PHASE 1 SAFETY TRIALS: Scientists give the vaccine to a small number of people to test safety and dosage as well as to confirm that it stimulates the immune system.
PHASE 2 EXPANDED TRIALS: Scientists give the vaccine to hundreds of people split into groups, such as children and the elderly, to see if the vaccine acts differently in them. These trials further test the vaccine’s safety and ability to stimulate the immune system.
PHASE 3 EFFICACY TRIALS: Scientists give the vaccine to thousands of people and wait to see how many become infected, compared with volunteers who received a placebo. These trials can determine if the vaccine protects against the coronavirus. In June, the F.D.A. said that a coronavirus vaccine would have to protect at least 50% of vaccinated people to be considered effective. In addition, Phase 3 trials are large enough to reveal evidence of relatively rare side effects that might be missed in earlier studies.
EARLY OR LIMITED APPROVAL: China and Russia have approved vaccines without waiting for the results of Phase 3 trials. Experts say the rushed process has serious risks.
APPROVAL: Regulators in each country review the trial results and decide whether to approve the vaccine or not. During a pandemic, a vaccine may receive emergency use authorization before getting formal approval. Once a vaccine is licensed, researchers continue to monitor people who receive it to make sure it’s safe and effective.
COMBINED PHASES: One way to accelerate vaccine development is to combine phases. Some coronavirus vaccines are now in Phase 1/2 trials, for example, in which they are tested for the first time on hundreds of people. (Note that our tracker would count a combined Phase 1/2 trial as both Phase 1 and Phase 2.)
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