FDA Warns Health Care Professionals Against Changes to Authorized Dosing Schedules of COVID-19 Vaccines

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In a new statement, the US Food and Drug Administration (FDA) recommended all health care professionals should continue to administer 2 full doses of the 2 vaccines currently available against the coronavirus disease 2019 (COVID-19).

The statement comes after discussions, including reports in the media, about altering the dosing schedule in order to immunize more individuals against COVID-19. Proposed alternatives include reducing the number of doses, extending the length of time between doses, changing the dose, or mixing and matching vaccines, according to the FDA.

The FDA has granted emergency use authorization for vaccines produced by Pfizer-BioNTech and Moderna.

“At this time, suggesting changes to the FDA-authorized dosing or schedules of these vaccines is premature and not rooted solidly in the available evidence. Without appropriate data supporting such changes in vaccine administration, we run a significant risk of placing public health at risk, undermining the historic vaccination efforts to protect the population from COVID-19,” said FDA Commissioner Stephen M. Hahn, MD, and Peter Marks, MD, PhD, director, Center for Biologics Evaluation and Research, FDA, in the statement.

Hahn and Marks noted that administering rating a single-dose regimen and/or administering less than the dose studied in clinical trials is concerning, “as there is some indication that the depth of the immune response is associated with the duration of protection provided.”

Although data from the phase 3 trials of both the Pfizer-BioNTech and Moderna COVID-19 vaccine suggested some protection following the first dose, the FDA cautioned that the participants who did not receive 2 vaccine doses at either a 3- or 4-week intervals were only followed for a short period of time.

“We cannot conclude anything definitive about the depth or duration of protection after a single dose of vaccine from the single dose percentages reported by the companies,” said Hahn and Marks.

The current available data continues to support the use of the 2 vaccines. For the Pfizer-BioNTech COVID-19 vaccine, the interval is 21 days between the first and second dose and 28 days between doses for the Moderna vaccine.

“We know that some of these discussions about changing the dosing schedule or dose are based on a belief that changing the dose or dosing schedule can help get more vaccine to the public faster,” concluded Hahn and Marks. “However, making such changes that are not supported by adequate scientific evidence may ultimately be counterproductive to public health.”