WASHINGTON • The US Food and Drug Administration (FDA) delivered a clear rebuke to health officials attempting to alter the timing and dosage of Covid-19 vaccines: Do not mess with our guidelines.
The agency, in a statement late on Monday, urged that vaccines be given according to how the FDA has authorised them after a key US official proposed cutting dosage levels for Moderna’s shot as a way to immunise 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-authorised 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 roll-out efforts as distribution has proven slower than expected.
Though the United States and other countries authorised 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.
Dr Moncef Slaoui, chief scientific officer of Operation Warp Speed, the US government’s vaccine drive, asked Moderna and the FDA to cut in half the dose of the company’s vaccination for people aged between 18 and 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 programme Face The Nation on Sunday.
Meanwhile, a British 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 and Moderna.
The FDA said the effectiveness seen in late-stage trials can be safely attained only if the shot developed by Pfizer and BioNTech is received at an interval of 21 days, and the one from Moderna is administered at an interval of 28 days.
Pfizer last week emphasised its vaccine should be delivered to individuals within the recommended three-week period.
Mr Hahn acknowledged that a small number of people in the Moderna and Pfizer trials did not follow the three-or four-week interval regimen, but these people were not 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 behaviour to take unnecessary risks,” Dr Peter Marks, director of the FDA office that oversees vaccines, said.
The coronavirus’ resurgence – aided by a faster-spreading strain – underscores the urgency to vaccinate more people as hospitals become overwhelmed.
Moderna on Monday lifted its production forecast, saying it will make at least 600 million doses of its shot this year.
AstraZeneca is conducting further studies on the vaccine it developed with the University of Oxford after initial results showed that a half dose followed by a full dose induced a higher protection rate than if a full dose was used in the first shot.
It is also considering studies to learn how effective inoculation can be when its candidate vaccines are combined with those developed by other companies.
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