People can schedule their second doses of Covid-19 vaccine up to six weeks after their first doses if they are otherwise unable to get one in the recommended timeframe, the US Centers for Disease Control and Prevention said in guidance updated Thursday.
The recommended time between doses is three weeks for Pfizer/BioNTech’s vaccine, and four weeks for Moderna’s vaccine.
"The second dose should be administered as close to the recommended interval as possible,” the latest guidance says.
"However, if it is not feasible to adhere to the recommended interval, the second dose of Pfizer-BioNTech and Moderna COVID-19 vaccines may be scheduled for administration up to 6 weeks (42 days) after the first dose. There are currently limited data on efficacy of mRNA COVID-19 vaccines administered beyond this window. If the second dose is administered beyond these intervals, there is no need to restart the series."
The updated CDC guidance appears to clarify earlier language that said “there is no maximum interval between the first and second doses for either vaccine.”
Delaying the second dose up to six weeks is in line with what WHO advisers said earlier this month.
CDC says its guidance may be updated as new information and new types of Covid-19 vaccines become available.
Fauci's response: Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said people would be "taking a chance" if they follow the CDC's updated guidance.
"You're taking a chance, the data from the clinical trials, showed that in the Moderna trial, you should get the boost 28 days after the prime, that's what I got, I got it exactly 28 days later, when you're dealing with Pfizer it's 21, that's where the data show is the optimal effect," Fauci told CNN Chris Cuomo on Thursday.
Fauci said it's possible that delaying the second dose is “not going to be a big deal.” However, he said, we don’t know for sure because the vaccine data hasn’t been looked at for this extended time-period between doses.