Considerations for unblinding individual study participants during vaccine trials.

Premature unblinding of individual participants is rarely reported in publications, but such unblinding can disrupt vaccine trials by causing worry and drop-out of other participants or "pseudo unblinding," in which participants or investigators over-interpret certain symptoms as being related to receiving an investigational product. This review summarizes appropriate reasons for unblinding in vaccine trials. Regulatory guidance could be improved by distinguishing guidance for vaccine trials from drug trials, with the recognition that unblinding individual participants in vaccine studies is rarely needed for management of adverse events following immunization.
Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: All authors received support from the Coalition for Epidemic Preparedness Innovations(CEPI) either directly or through a grant administered by the Task Force for Child Survival. NH reports ongoing support from Hillevax and Takeda, and past support from Pfizer, Valneva, and Inovio for service on safety reviews or DSMBs, and support from ILiAD Biotechnologies for an advisory board. CD reports a relationship with Dynavax Technologies Corporation that includes equity or stocks and service on a Scientific Advisory Board for Medicago. MD reports current research support from Merck and previous research support from Walgreens. CW reports suppoort from Moderna Inc that includes consulting or advisory. UH reports support from Pfizer Inc, Sanofi Aventis France, InfectoPharm Medicines and Advice GmbH that includes: speaking and lecture fees, from Takeda Switzerland and HilleVax that includes consulting or advisory. KE reports support from Pfizer, Moderna, GSK, Seqirus, Merck; Roche, Sanofi for sevice on advisory committees or DSMBs and consulting fees from Bionet and X-4 Pharma.WO serves as an uncompensated member of the Moderna Scientific Advisory Board. CW reports support from Moderna. MS reports consulting, advisory, or speaking and lecture fees with Pfizer, GlaxoSmithKline, Sanofi, Merck & Co Inc, AstraZeneca Pharmaceuticals LP, Janssen Pharmaceuticals Inc and board membership with Janssen. AH, RC, JB, SE, JE, NKA,SO,YJ, NB and PP report no conflicts.
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