(Reuters) - Pfizer Inc PFE.N and Johnson & Johnson JNJ.N are seeking input from a U.S. Food and Drug Administration advisory committee on retaining and attracting volunteers for COVID-19 vaccine trials after a vaccine becomes available, if they know they might receive a placebo.
Both U.S. companies are among a handful with pivotal, late-stage COVID-19 vaccine trials underway.
The comments in letters ahead of the meeting of expert advisers on Thursday underscore dilemmas facing leading coronavirus vaccine developers and those whose large trials are just beginning or being planned.
Drugmakers are racing to find vaccines to protect against the coronavirus that has caused more than 1 million deaths globally. Many have begun trials involving tens of thousands of people who receive either an experimental vaccine or a placebo without knowing which.
J&J, in its comments, said a discussion is needed on the potential challenges of maintaining trial enrollment in ongoing large studies, especially after initial vaccines become available.
It is likely several vaccines will be needed to inoculate billions of people around the world.
The company said that once the first vaccines are licensed or authorized, it may lead volunteers to seek available vaccines instead of participating in ongoing trials. Volunteers already enrolled in trials might withdraw, it warned.
Pfizer, which is developing its vaccine with Germany's BioNTech SE 22UAy.F, could provide early data from their late-stage vaccine trial later this month. Moderna Inc MRNA.O is likely to have early data on its candidate in November.
The FDA will then consider whether to issue a quick emergency use authorization (EUA), given the desperate need for a vaccine, or seek additional data before making a decision.
J&J is a step behind after its U.S. trial was paused earlier this month due to an illness in a study participant. AstraZeneca's AZN.L U.S. vaccine trial is also paused due to an illness in its UK trial, but is expected to resume as soon as this week, Reuters reported, citing four sources.
In its guidance on EUAs for vaccines, the FDA said earlier in October that a drugmaker should continue to collect data in any ongoing trials for as long as feasible, even after getting an authorization, and work toward submission of a formal approval application as soon as possible.
Pfizer said it may have an ethical duty to inform at least some study volunteers that they have been given a placebo. It has proposed allowing them to move over to the vaccine arm of the study should its vaccine receive an EUA. (bit.ly/3dQqSxP)
J&J said it was evaluating a number of measures aimed at retaining trial volunteers.
"It would be helpful if FDA could share insights at the upcoming (meeting) on potential options they believe can be acceptable," J&J said. (bit.ly/37vCKEl)
Reporting by Ankur Banerjee in Bengaluru, Julie Steenhuysen in Chicago and Michael Erman in New York; editing by Caroline Humer and Bill Berkrot
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