In February 2023 Pfizer and Valneva announced that Pfizer, study sponsor of the VALOR Phase III clinical study, has decided to “discontinue a significant percentage of participants in the US” who had been enrolled already.  

This discontinuation represents “approximately half of the total recruited participants” and is due to “violations of Good Clinical Practice (GCP) at “certain clinical trial sites”. The statement from Pfizer and Valneva emphasises that these were run by a “third-party clinical trial site operator”. Furthermore, the discontinuation was not caused by safety concerns associated with the vaccine candidate.  

GCP and violations 

GCP is internationally recognised as a set of requirements to uphold ethical and scientific quality in clinical trials. Valneva states that they put “participants’ interests first and ensure high scientific integrity”.  

Pfizer learnt of “potential violations” and responded with a “thorough review” of both operations and data collections, following “standard operating safeguards” to determine the “correct course of action”.  

Consequences for the trial 

The joint statement suggests that the wider trial is ongoing with other sites that are not managed by the third party responsible for these violations and continues to enrol new participants. Participants are being notified, and Pfizer has also notified the appropriate regulatory agencies and the independent Institutional Review Board for the study.  

“Integrity of data collected in clinical trials is critical to provide evidence and confidence in a potential vaccine or medicine’s safety and efficacy.” 

Pfizer and Valneva are “committed to collecting robust data” in order to achieve regulatory submission of VLA15, the candidate in investigation. As we have previously explored, strong immunogenicity data were reported from Phase II studies.  

We will hear more from representatives of Pfizer and Valneva at the Congress in Washington this April, as well as specific sessions on improving clinical trial procedures and outcomes.