The October Surprise? Covid Vaccines Will Not Be Expedited by an EUA - Dr. Peter Marks, FDA 
(Thursday, October 29, 2020]​
The data needed to support an EUA will be almost identical to that required for a BLA for the Covid vaccines being developed, according to Dr. Peter Marks, Director of CBER, FDA. This is a major shift (read “clarification”) from the public perception of when Covid vaccines may be available in the US. It has been generally assumed that manufacturers would start filing EUA applications for their vaccines before the clinical trials are completed with the first EUA coming as early as in 4 weeks at the end of Nov, and more than one EUAs by the end of the year. But that may not lead to the quick approval of these vaccines. Dr. Marks clarified that since these vaccines will be given to healthy individuals, “FDA will only issue an EUA if a vaccine has demonstrated clear and compelling efficacy in a large well-designed Phase 3 clinical trial, much like would be required for a BLA.” The process of FDA review of vaccine clinical trial data will not be rushed, and FDA will not allow any shortcuts in trials. Several vaccines are being evaluated in large Phase 3 trials involving 30,000 or more participants, and these trials may provide adequate evidence of the efficacy of these vaccines provided there are enough incidences of post-vaccination viral exposure in the tested populations. FDA has set a relatively modest standard of 50% response in vaccinated populations, basically that about 50% more participants in the vaccinated population compared to the control population should be protected from infection. The best way to evaluate a vaccine is by doing challenge studies where vaccinated individuals are deliberately exposed to the virus to measure protection. No such challenge studies are planned in the US at this time, however, one challenge study is being reviewed by the regulators in the UK. Challenge trials are generally smaller is size, involving 50-500 volunteers but carry significant ethical concerns particularly when the pathogen being evaluated is deadly with no cure, such as the SARS-CoV-2 virus. The alternate is to vaccinate thousands of individuals and wait for several to be naturally infected, an unpredictable process based on infection incidence rates in the vaccinated populations. Either way, any vaccine that shows promising results in clinical trials would be diligently reviewed by the FDA and presented to the Vaccine Advisory Committee prior to the decision by FDA. All of these steps pretty much guarantees no vaccine approvals before the end of the year and potentially much into next year. Although the above FDA policy was disclosed in an opinion piece in a newspaper and not FDA’s formal channels, the source of the news confirms that FDA will rather take a well-beaten path to Covid vaccine than to trailblaze a new one.