Researchers say drug companies need to be more open about how vaccine trials are run to reassure Americans who are skittish about getting a coronavirus vaccine.

The morning after the world learned that a closely watched clinical trial of a coronavirus vaccine had been halted last week over safety concerns, the company’s chief executive disclosed that a person given the vaccine had experienced serious neurological symptoms.

But the remarks weren’t public. Instead, the chief executive, Pascal Soriot of AstraZeneca, spoke at a closed meeting organized by J.P. Morgan, the investment bank.

AstraZeneca said on Saturday that an outside panel had cleared its trial in Britain to begin again, but the company still has not given any details about the patient’s medical condition, nor has it released a transcript of Mr. Soriot’s remarks to investors, which were reported by the news outlet STAT and later confirmed by an analyst for J.P. Morgan.