Approval of COVID-19 vaccines will change nature of clinical trials


While stressing the urgent need to vaccinate the whole U.S. population, infectious disease experts and medical ethicists are raising questions about the clinical trials needed to answer important questions about the new COVID-19 vaccines.

In a statement released on Nov. 20, Barbara Alexander, MD, president of the Infectious Diseases Society of America (IDSA) and a professor at Duke University, Durham, N.C., commented on Pfizer and BioNTech’s application to the Food and Drug Administration for an emergency use authorization (EUA) for its COVID-19 vaccine. Besides emphasizing the need for a transparent review of the companies’ trial data prior to the FDA’s granting an EUA, she said, “If emergency use authorization is granted, clinical trials and data collection must continue.”

In an interview, Dr. Alexander said she is convinced that both Pfizer and Moderna, which is also expected to seek an EUA soon, will continue their clinical trials to monitor the long-term safety and efficacy of their vaccines.

“The EUA guidance for COVID vaccine authorization is very clear that clinical trials will move forward,” she said. “Any EUA request would have to include a strategy to ensure that the long-term safety and efficacy of a vaccine could be monitored. I see no evidence that either Pfizer or Moderna is not prepared to follow those regulations.”

Eventually, she added, the drug makers will have to seek full FDA approval to replace an EUA, which as its name signifies, is designed for public health emergencies. “The EUA is a tool to help us get the vaccine into circulation and have it start working as quickly as possible in the current health crisis,” she said. “But once the crisis is over, if the sponsors want to continue to market their vaccines, they have to go forward and get full approval.”

Medical ethicists, however, point out there may be ethical and practical dilemmas involved in continuing or initiating clinical trials once a vaccine has been approved for use even on an emergency basis.

In a commentary in Annals of Internal Medicine, Rafael Dal-Re, MD, PhD, Arthur L. Caplan, PhD, and two other ethicists stipulated that the pandemic requires early licensing and deployment of COVID-19 vaccines. Nevertheless, they noted, additional months of data are required to establish the long-term efficacy and safety of the vaccines. “Moreover, early deployment could interfere with the acquisition of long-term data,” both on these vaccines and on others coming through the pipeline, they wrote.

In countries where an approved vaccine is deployed, the ethicists noted, investigators must inform participants in an ongoing trial about the approved vaccine’s status and ask if they want to continue in the study. If enough participants decline, the trial might have to be terminated early. At that point, researchers may not have sufficient long-term data to identify late-term safety issues, determine how long efficacy lasts, determine whether waning immunity is associated with reduced levels of antibodies, or identify the level of neutralizing antibodies that correlates with immunity.

Moreover, they observed, long-term trials are especially important for vaccines that use mRNA technology, because less is known about them than about traditional kinds of vaccines.

The authors also pointed out that early licensing of any vaccine might make it harder to evaluate vaccines that haven’t yet been approved. “Once a vaccine is licensed, new placebo-controlled RCTs [randomized controlled trials] of other vaccines will not be acceptable ethically, and noninferiority RCTs will be the most likely alternative.

“The goal of noninferiority trials will be to demonstrate that the immune response (that is, neutralizing antibody titers or levels) of the candidate vaccine is not inferior to that of the approved vaccine within a prespecified margin, which the FDA has established as less than 10% for COVID-19 vaccines,” the authors noted.


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