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FDA will not alter dosing schedules for authorised COVID-19 vaccines

Time period between first and second vaccines has been extended in the UK

The US Food and Drug Administration (FDA) will not make any changes to dosing or schedules for authorised COVID-19 vaccines, in a move that differs to the UK’s recent decision.

In the UK, health authorities have decided that they will increase the time period between vaccine doses for up to 12 weeks, as opposed to the recommended three or four weeks.

The aim of increasing the time between the doses is to ensure that more people are able to be vaccinated, with the hopes of protecting a larger proportion of people from COVID-19.

A report from the New York Times also suggested that British regulators were allowing for the mixing of doses of two, separate vaccines, although this has since been refuted by Public Health England (PHE).

“We do not recommend mixing the COVID-19 vaccines – if your first dose is the Pfizer vaccine you should not be given the AstraZeneca vaccine for your second dose and vice versa,” said Mary Ramsay, head of immunisations at PHE.

“There may be extremely rare occasions where the same vaccine is not available, or where it is not known which vaccine the patient received.

“Every effort should be made to give them the same vaccine, but where this is not possible it is better to give a second dose of another vaccine than not at all,” she added.

The FDA, which said in a statement that it has “been following the discussions and news reports about reducing the number of doses, extending the length of time between doses, changing the dose (half-dose), or mixing and matching vaccines”, maintains that such changes are “premature and not rooted solidly in the available evidence”.

This means that it will not recommend changing the dosing schedules of the  Pfizer/BioNTech and Moderna COVID-19 vaccines that have both received an FDA emergency use authorisation (EUA).

For the Pfizer/BioNTech vaccine, the recommended interval between the first and second dose is 21 days, while the two doses of the Moderna vaccine are recommended to be given 28 days apart.

The FDA has argued that the available data only supports using the two specified doses of the authorised vaccines at the specified intervals.

“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,” commented the FDA.

“However, making such changes that are not supported by adequate scientific evidence may ultimately be counterproductive to public health,” the agency added.

Article by
Lucy Parsons

5th January 2021

From: Regulatory



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