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Vaccine Fever

Vaccine fever has gripped the nation. Everyone is talking about the COVID-19 vaccine. EVERYONE. People who want it right now. People who swear they’ll never get it. People who might get it but aren’t sure if it’s safe. Politicians. Doctors. Employers. Superintendents. EVERYONE. A vaccine would be a way out of this pandemic, so of course it’s a hot topic of conversation. However, creating and testing a vaccine is a long and complicated process and necessarily so.

Vaccines are some of the safest and most effective medical interventions that we have. That’s because they go through multiple clinical trials. In fact, the CDC identifies six different stages for vaccine development.1 However, there is one stage that everyone is laser focused on right now: clinical development. Within the clinical development stage, there are four phases. Phase I includes small groups of people who receive the trial vaccine, typically 20-100 people.2 Phase II involves expanding the number of and types of people (varying in age, health status, etc.) who receive the trial vaccine but the groups are still kept fairly small, usually somewhere in the hundreds. Phase III involves expanding the trial vaccine to thousands of people and is where the efficacy and safety are tested. Phase IV is optional, and includes additional trials after the vaccine has been approved and licensed. As of early October, 2020, there are 11 trial vaccines that are in Phase III of the clinical development stage.3 That means that thousands of people have been given the trial vaccines.

Phase III is incredibly important in vaccine development because efficacy, which looks at if the vaccine prevents people from catching the disease, and safety are really determined in this phase. In Phase III, thousands of volunteers are recruited. Some of them receive the trial vaccine and some of them receive a placebo. Then those volunteers are tracked over time to see how many of them contract the disease, in this case COVID-19. Then, the number of infections between the group who received the trial vaccine is compared against the number of infections in the group who received the placebo. That’s how the efficacy part is determined. The safety component to the vaccine is determined through adverse event tracking, meaning – did the trial vaccine cause any unwanted side effects in people and if so, what and how frequently?

Determining efficacy and safety takes time, but taking that time is ultimately what has made vaccines so safe and effective. If a vaccine completes Phase III and goes to market, it’s because it was both safe and effective, which is what we want and need. Mistrust of science and especially vaccines runs rampant through our society and rushing a Phase III would only exacerbate those feelings, and for good reason. Developing a vaccine is a huge responsibility, especially in the middle of a pandemic. That’s why it’s so important that we get it right. It can be frustrating to wait, but if we are patient, we may end up with a vaccine that, like others (e.g., smallpox, polio), helps us to eliminate the threat of the disease completely. Think about what that world looks like. A world where COVID-19 was eradicated sounds pretty good right now.


  1. Centers for Disease Control and Prevention. Vaccines and Immunizations. Vaccine Testing and the Approval Process.
  2. Food and Drug Administration. Ensuring the Safety of Vaccines in the United States.,%20blood%20%26%20biologics/published/Ensuring-the-Safety-of-Vaccines-in-the-United-States.pdf
  3. The New York Times. Coronavirus Vaccine Tracker. By Jonathan Corum, Sui-Lee Wee, and Carl Zimmer.