A large, pivotal study of Moderna Inc.'s Covid-19 vaccine could yield a preliminary answer about whether the shot works safely as early as October, though it's more likely to be November, the company's leader said.
Moderna Chief Executive Stephane Bancel said in an interview the timing will depend on rates of infection in the U.S. locations where the trial is being conducted, because the study is comparing whether fewer vaccinated people come down with symptomatic Covid-19 than unvaccinated people.
Researchers will assess this at intervals after a certain number of cases occur, ranging from 53 cases to 151 cases.
"Thankfully for the U.S. population it has become better the last few weeks," he said, referring to a general decline in new cases since August. "That actually makes it harder for an October readout on efficacy of the vaccine."
His remarks suggest that Moderna and Pfizer Inc. executives have similar goals for getting key data from final-stage trials for their respective vaccine candidates. Pfizer Chief Executive Albert Bourla, in recent television interviews, also gave an end-October time frame. Its vaccine is being developed with partner BioNTech SE.
If Moderna's interim results are positive, the company could seek government authorization for emergency use of the vaccine soon thereafter, Mr. Bancel said. That could lead to quick distribution of any available doses, which Moderna has been manufacturing.
The U.S. government has told states to be ready to help distribute one or more Covid-19 vaccines as early as late October or November, though some officials, including National Institute for Allergy and Infectious Diseases Director Anthony Fauci, have said it could be later in the year.
Even if the trials provide positive results this fall, most people wouldn't be able to get vaccinated until next year because supplies will be limited early on.
Moderna and Pfizer have two of the leading vaccine candidates. The Phase 3 trial for another advanced vaccine candidate is halted in the U.S. and many other countries due to an unspecified safety incident, though testing has resumed in the U.K.
Moderna's late stage, or Phase 3, trial has enrolled more than 25,000 people since starting the federally funded trial in July, toward a goal of 30,000.
Also Thursday, Moderna publicly posted the 135-page protocol for the clinical trial, which the company says will provide transparency around its rapid development efforts.
The Moderna protocol spells out how the trial is being conducted, including the involvement of an independent committee that monitors data as the trial progresses and can recommend halting it if safety issues arise. The committee can also recommend halting the trial at interim points if the vaccine is clearly effective.
"We want to be part of the solution," Mr. Bancel said. "We're working hard for nine months to get a safe vaccine to the marketplace. Credibility and transparency are really important."
As many people as possible will need to be vaccinated to prevent the spread of the new coronavirus and allow businesses and schools to fully reopen, health authorities and industry officials say, but large percentages tell pollsters they have safety and other concerns.
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