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How vaccines get made and approved in the US

  • Recruiting clinical trial participants

    Once a new drug is deemed safe for humans, it must be tested on humans in order to prove its efficacy and solidify its safety. A number of potential COVID-19 vaccines are already being tested on humans. However, recruiting participants is not always easy. This has been shown in the case of COVID-19 trials having difficulty recruiting Black trial participants. This is perhaps unsurprising, as Black communities have experienced medical misconduct in the past, such as the Tuskegee experiments.

  • Control vs. experimental groups

    When enough human participants are found, the new potential vaccine is put through a randomized clinical trial, where people in the group are assigned to either a control or experimental group. The experimental group gets the vaccine, while the control group gets a placebo. Neither the people themselves nor the researchers know which group the participants are in. This does away with bias, and it is only at the end of the study that the researchers and participants find out who was in which group.

  • Phase 1 clinical trial

    During phase 1 of the clinical trial, the first participants receive the vaccine being tested. The objectives of this phase are to evaluate the vaccine’s safety and its ability to produce the desired immune responses. It is often during this phase that the mode of giving the vaccine and the immunization schedule (how often to give the vaccine) are also assessed.

  • Peer review of trial results

    Once a trial has results, these results must be peer reviewed. This means that expert scientists go over the data to make sure it is correct and reproducible. There have already been multiple COVID-19 vaccine candidates where phase 1 and 2 trials stood up to peer review.

  • Phase 2 clinical trial

    Once a candidate achieves satisfactory safety and immune response outcomes in phase 1, it moves onto the phase 2 clinical trial. Phase 2 leaves the controlled clinical setting and moves into field evaluation. This requires a steeper financial investment and therefore stricter stop-and-go policies are observed by the drug developers.


  • Phase 3 clinical trial

    After the drug performs successfully in phase 2, it moves into the pivotal phase 3 trials, which are essential for the registration and market approval of a vaccine. These are designed to evaluate efficacy and safety. These large-scale clinical trials enroll thousands of subjects and are conducted in conditions that will be similar to the future routine use of the vaccine.

  • Clinical trial pause

    While a lot of attention has been given to pauses in COVID-19 vaccine clinical trials, these pauses are in fact signs that the system is working and science is progressing as it should, not that vaccines are dangerous. Because vaccines are given to otherwise completely healthy people, there is a high bar for trials testing vaccines to make sure they are completely safe. Therefore, if a test participant becomes ill for any reason during a trial, the trial is paused to examine the cause of the illness.

  • Interim analysis

    An interim analysis is done as the trial progresses in order to evaluate the effectiveness of the vaccine. In order to do an interim analysis, there need to have been enough cases of the illness among the participants to analyze the percentage that took place in the control groups as compared with the vaccinated group. The most recent COVID-19 vaccine candidate from Moderna showed a 94% success rate in its interim analysis, with only five of 95 cases of COVID-19 occurring in the vaccinated group.

  • Clinical trial stop

    Because clinical trials are vital to progress in medicine, it is imperative that they are conducted safely. Therefore, when any ethical or safety issues are raised in the testing of a vaccine, the clinical trial is often stopped. According to the article Bioethics in Practice: Considerations for Stopping a Clinical Trial Early, “The early-stopping rule has the potential to minimize harm and to maximize benefit for the patients enrolled in a randomized trial.”

  • Biologics License Application

    A Biologics License Application (BLA) is required to gain permission to enter a biologic product into interstate commerce. This application requires information from the applicant, who can be any legal person or entity engaged in manufacturing, along with information about the product, preclinical study information, and labeling.