Fauci says he’s worried about delaying second vaccine dose

U.S. infectious-disease chief Anthony Fauci said he’s worried about a push to delay administering the second dose of COVID-19 vaccines 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. Delaying the second shot could also give rise to more mutated forms of the virus, the NIAID chief said.

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 followup doses could be given up to six weeks later.

The U.K. was first to adopt the controversial approach. Shots made by Pfizer Inc. with BioNTech SE and by 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. Another vaccine, developed by the University of Oxford and AstraZeneca Plc, was tested with broader gaps between the two shots.

The rush to broaden vaccinations to as many as people as possible in the first instance comes amid concern about the new strains. The U.K. has said that one variant that was first identified there could be more contagious as well as deadlier. Another one that’s spreading in South Africa has shown that it may be more resistant to vaccines.

“There seems to be considerable more threat to vaccine efficacy, even though the cushion of efficacy is sound enough that the vaccines we’re using now will be good against both the mutant in South Africa as well as those in the U.K.,” Fauci said.

Vaccine developers need to look at tweaking shots to address the new variants, Fauci said. Researchers and other health officials have said that could generally be done within weeks for many shots.

Fauci has vaulted back onto the international scene since U.S. President Joe Biden’s inauguration last week, speaking to the media about being disparaged under the Trump administration and pledging his country’s renewed commitment to the World Health Organization.