Defining COVID-19 Terms: Clinical Trial

May 21, 2020


Elizabeth (Izzy) Montgomery, MPA
Policy Analyst

  • Subscribe for Updates

In this installment in our series explaining key terms and phrases used by public health officials in discussions of the COVID-19 pandemic, we look at the term “clinical trial.”

Clinical trials are a vital component of the development process for medications, vaccines, and other medical treatments and preventatives, including those for COVID-19. Medication combinations and new uses for current medications may also be evaluated in a clinical trial.

A clinical trial is a type of study in which researchers test novel approaches to prevent, detect, or treat disease. Clinical trials include four distinct phases:

  • Phase 1: The objectives of this phase are to determine whether the intervention being tested is safe and determine an appropriate dosage. Usually, fewer than 100 healthy people receive the intervention and are closely observed to identify any adverse reactions or side effects.
  • Phase 2: In this phase, the objective shifts to testing whether an intervention works in treating a particular condition, and the trial enrolls people with that condition. At this stage, more people may receive the intervention (usually 100‒300). Researchers continue to monitor side effects and gather other key information they need to begin designing Phase 3 of the clinical trial.
  • Phase 3: The objective of this phase is to prove that an intervention works in treating the condition, particularly when compared to other existing treatments for the same condition. This phase requires randomization ― for example, giving some participants the new medication being tested and giving other participants an existing medication used to treat the disease. Side effects continue to be monitored, and researchers may enroll as many participants as the study design requires at this stage, often 1,000 or more.
  • Phase 4: At this point, the intervention has been approved by regulatory agencies and can be marketed. Entities such as the Food and Drug Administration (FDA) continue to collect data to assess the long-term side effects experienced by those who receive the treatment.

According to a vaccine tracker created by the Milken Institute, eight vaccines for COVID-19 are currently in clinical trials, with many more in the pre-clinical trial stage. However, one vaccine in particular has made . The National Institute of Allergy and Infectious Diseases, an institute within the U.S. Department of Health and Human Services, is currently in Phase 1 of a clinical trial to evaluate an investigational vaccine co-developed with Moderna, Inc. On Monday, May 18, Moderna announced in a press release that early data demonstrated that the vaccine triggered an immune response to COVID-19 in participants. The FDA recently gave Moderna permission to begin Phase II of the clinical trial for the vaccine, known as mRNA-1273. Depending on their efficacy, some investigational COVID-19 vaccines could receive emergency use authorization from the FDA later this year, possibly creating a mechanism for the vaccine to be tested among high-risk people such as frontline healthcare workers.

See more definitions of terms and other information about the pandemic on our website’s COVID-19 in Arkansas page.

    Skip to content