(Bloomberg) -- U.S. infectious-disease chief Anthony Fauci said he’s worried about delays to the second dose of Covid-19 vaccinations as governments stretch intervals in an effort to speed immunizations.
Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, said Monday that it’s best to give shots in line with schedules outlined in clinical trials.
“I’d be concerned, because you don’t get full efficacy until you get that second dose,” Fauci said on a virtual World Economic Forum panel moderated by Bloomberg’s editor in chief, John Micklethwait.
Governments around the world are scrambling to boost vaccination programs to curb the worrisome spread of new variants. France on Saturday recommended doubling the amount of time between the first and second shots, days after the U.S. Centers for Disease Control and Prevention said the follow-up doses could be given up to six weeks later.
The U.K. was first to adopt the controversial approach. The shots made by Pfizer Inc., BioNTech SE and Moderna Inc. were designed and tested with two inoculations, 21 or 28 days apart. There are no data to demonstrate that protection from the first dose is sustained after the date of the second injection.
In early January, Fauci said he wouldn’t be in favor of delaying the second dose.