7 Nov 2017 FDA VRBPAC: Clinical development plan for a S. aureus vaccine (Part 1 of 3)

Addendum: This is the first in a 3-newsletters series on this topic. Go here and here for the next two newsletters. Finally, the results of the STRIVE trial have been published as Hassanzadeh et al. in Clinical Infectious Diseases, ciad218, https://doi.org/10.1093/cid/ciad218.

Dear All: 

I just learned that FDA’s Vaccines and Related Biological Products Committee (VRBPAC) will meet at White Oak in an open session on 7 Nov 2017 to discuss and make recommendations on the clinical development plan for Pfizer’s investigational Staphylococcus aureus vaccine intended for pre-surgical prophylaxis in elective orthopedic surgical populations. The only materials available are the announcement at this link — more materials are promised no less than 2 business days in advance.

This is really interesting to see. We’ve had prior debates on this topic that have revolved around these questions:

  1. Can you use eradication of carriage as a measure of the value of prophylactic agent?
  2. How big does the study have to be if you must show reduction in a serious (non-trivial) clinical infection?
  3. In what population can you do this?


In general the answers to date have been NO, VERY LARGE, and NOT SURE. The answer of NO for Q1 is well stated in the 23 Oct 2013 EMA Addendum (Section 3.5.3): Indications that relate to the reduction or eradication of a pathogen from a specified body site are not acceptable unless the microbiological effect of active treatment has been shown to result in a measurable clinical benefit. In the absence of adequate data to support such a link, the clinical benefit associated with the effect of treatment on carriage should be demonstrated in a placebo-controlled study with a primary clinical endpoint.

The final NOT SURE answer follows in part because the moment you identify a group at real risk, there is an ethical requirement to do everything you can to reduce the rate of infection (e.g., use really good peri-operative antibiotic prophylaxis). And the VERY LARGE follows from the need to then limit studies to a setting where the risk of infection is low!

Although it is important that we have tools of this type, the difficulties implied by these answers have stymied work to date. I am delighted to see this VRBPAC announcement and look forward to hearing the discussion!

All best wishes, –jr

John H. Rex, MD | Chief Medical Officer, F2G Ltd. | Expert-in-Residence, Wellcome Trust. Follow me on Twitter: @JohnRex_NewAbx. See past newsletters and subscribe for the future: https://amr.solutions/blog/

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