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What do you make of the AstraZeneka vaccine trial pause?

Question: What do you make of the AstraZeneka vaccine trial pause?

Answer: STATNews, which you cite in your question, broke this story yesterday and offers a good description of the issue. The AP’s reporting published this morning is also quite insightful. For those of you who haven’t read the reports, here’s a brief synthesis — AstraZeneka just paused its phase 3 clinical trial of its candidate vaccine because of a serious adverse reaction experienced by one of the participants. The Data Safety Monitoring Board (DSMB) is reviewing to make a determination. Bulleted below is a bit more information about the AstraZeneka candidate vaccine and about how DSMBs work.

As to my own thoughts — optimistic me thinks this is a good thing because: a) it shows that the scientific process is working as it should and that politics aren’t overriding safety protocols; b) it reminds us why clinical trials are so important before widespread roll out of any vaccine (or treatment); and c) it gives us some grounding by reminding us that vaccine development is challenging and that expedited timelines represent best-case scenarios. For those of you who may be more pessimistic, I’d remind you that at this stage, it’s unclear whether the adverse event was caused by or related to the vaccine; it could be a spurious association. We’ll know more after the DSMB reviews the data and makes a determination. In the meantime, don’t despair! This is the scientific process at work.

More Information on the Candidate Vaccine

  • AstraZeneka and the University of Oxford have partnered to develop a new vaccine, known as AZD1222. The type of vaccine is called a viral vector vaccine. It uses a harmless virus with pieces of SARS-CoV-2 DNA to teach/prime the immune system to attack SARS-CoV-2 if it ever enters the body.
  • Data from phase 1/2 clinical trial were recently shared in the Lancet. Results showed that the candidate vaccine produced intended antibody response and that mild/moderate side effects were reported among 60% of participants, but none were severe.
  • AstraZeneka is in phase 3 clinical trial for its candidate vaccine, and has been aiming to recruit 300,000 participants in the US, as well as participants in the UK. Two other phase 3 clinical trials are also underway for Moderna and BioNTech/Pfizer.
  • The US Government has invested at least $1.2 billion to help speed the development of AZD1222 and to reserve 400 million doses of the vaccine if/when it is ready.

More information on Data Safety Monitoring Boards (DSMBs)

  • The National Institutes of Health offers an overview of DSMBs here, but it’s not the most reader friendly description. The HIV advocacy group, AVAC, offers a more reader-friendly version here.
  • DSMBs are composed of independent experts, ethicists, and oftentimes community members who are not affiliated with the clinical trial and have no financial or other conflicts of interest. They review data from the clinical trial as it progresses to ensure that it is ethical to continue. This is extremely important because most clinical trials are double-blind meaning neither the participant nor the researcher knows what intervention (in this case, vaccine or placebo) they are receiving.
  • We need the DSMB to review as the study progresses whether a) there is an overwhelming positive effect that would cause the study to end early because it would be unethical to continue giving participants the inferior intervention; b) there is harm caused to the participants receiving the intervention that outweighs the benefits of the intervention, which would cause the study to end early because it would be unethical to proceed (the DSMB must make a risk/benefit calculation); c) futility of continuing, meaning that the trial as designed will not answer the study question.