With funding from the National Institutes of Health, the investigators plan to inoculate participants with potential vaccines and then to inject them with small doses of the Zika virus to test the vaccines’ effectiveness. The N.I.H. has not yet decided whether the research will proceed.

The scientists leading the trial say it is necessary to prevent a future epidemic. But Ms. Shah and other bioethicists convened by the N.I.H. concluded in 2017 that the research had “insufficient value” to justify the risks.

People outside the study, such as sexual partners, might also be infected, the panel said. And Zika infection might have unspecified consequences for participants in the long term.

But scientists in charge of the study said the panel’s concerns were hypothetical and did not take into account the proposed protocol. They plan to use minimal doses of Zika virus and to quarantine patients in a hospital inpatient unit.

The study also would start by enrolling only women — who are less likely to transmit Zika sexually — and would require them to use long-term birth control.