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FDA sends rebuke to officials seeking to alter vaccine regimen

A clinical pharmacist prepared to administer a shot of the Moderna COVID-19 vaccine on December 21, 2020, in Seattle, Washington.Karen Ducey/Getty

The U.S. Food and Drug Administration delivered a clear rebuke to health officials attempting to alter the timing and dosage of COVID-19 vaccines: Don’t mess with our guidelines.

The agency, in a statement late Monday, urged that vaccines be given according to how the FDA has authorized them after a key U.S. official proposed cutting dosage levels for Moderna Inc.’s shot as a way to immunize more people. Governments and health officials have also considered extending the length of time between doses or mixing and matching vaccines.

“Suggesting changes to the FDA-authorized dosing or schedules of these vaccines is premature and not rooted solidly in the available evidence,” FDA Commissioner Stephen Hahn said. He warned that such changes may not guarantee the high level of protection observed in the clinical trials, running a “significant risk” of endangering public health and undermining vaccination efforts.


Governments around the globe are trying to accelerate vaccine rollout efforts as distribution has proven slower than expected. Though the U.S. and other countries authorized some vaccines at unprecedented speed and have stockpiled hundreds of millions of doses, the pace of actual inoculations has been challenged by unexpected glitches and logistical problems.

Moncef Slaoui, chief scientific officer of Operation Warp Speed, the U.S. government’s vaccine drive, asked Moderna and the FDA to cut in half the dose of the company’s vaccination for people 18 to 55 after finding evidence that it induces the same immune response. That would double the amount of vaccine available for the age group, while providing the same level of protection, he said on CBS’s “Face the Nation” on Sunday.

Meanwhile, a U.K. plan would allow for second doses of vaccines to be administered as many as 12 weeks after the first, longer than the timing determined as optimal for shots developed by Pfizer Inc. and Moderna.


The FDA said that the effectiveness seen in late-stage trials can only be safely attained if the shot co-developed by Pfizer and BioNTech SE is received at an interval of 21 days, and the one from Moderna is administered at an interval of 28 days. Pfizer last week emphasized its vaccine should be delivered to individuals within the recommended three-week period.

Hahn acknowledged that a small number of people in the Moderna and Pfizer trials didn’t followed the three or four-week interval regimen, but those people weren’t followed long enough for any definitive conclusions about the depth and duration of protection.

“If people do not truly know how protective a vaccine is, there is the potential for harm because they may assume that they are fully protected when they are not, and accordingly, alter their behavior to take unnecessary risks,” Peter Marks, director of the FDA office that oversees vaccines, said in the statement.

The coronavirus’s resurgence -- aided by a faster spreading strain -- underscores the urgency to vaccinate more people as hospitals become stretched beyond their limits. Moderna on Monday lifted its production forecast, saying it will make at least 600 million doses of its shot in 2021.

AstraZeneca Plc is conducting further studies on the vaccine it co-developed with University of Oxford after initial results show a half dose followed by a full dose has induced a higher protection rate than if a full dose was used in the first shot. It’s also considering studies to learn how effective inoculation can be when its candidate vaccines are combined with those developed by other companies.