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COVID-19 : Coronavirus | Researchers urge delay of second dose of Pfizer vaccine

The first dose of the vaccine developed by Pifzer and BioNTech could present a 92.6% efficiency, and not 52.4% as originally thought, according to Danuta Skowronski, chief of Influenza Epidemiology and Emerging Respiratory Pathogens at the British Columbia Center for Disease Control (BCCDC) of Canada, and Gaston De Serres, epidemiologist at the National Institute of Québec Public Health.

Therefore, both researchers urge governments to delay the administration of the second dose to give the first injection to as many people as possible given the current shortage of vaccines.

Little short-term benefit

In a letter published Wednesday in the scientific journal The New England Journal of (NEJM) Medicine, experts suggest that “with such a protective first dose, benefits derived from a short supply of vaccine could be maximized by postponing second doses until all members of the priority group are offered at least one dose. “

In this sense, although they recognize that “there may be uncertainty about the duration of protection with a single dose”, they assure that “the administration of a second dose within 1 month after the first, as recommended, provides little short-term additional benefit“While high-risk people who miss the first dose are” completely unprotected. “

“Given the current shortage of vaccines, the postponement of the second dose is a national security issue which, if ignored, will surely result in thousands of hospitalizations and deaths related to COVID-19 this winter in America. Hospitalizations and deaths that would have been prevented with a first dose of vaccine ”, they sentence.

Pfizer delegates responsibility to health authorities

Pfizer has been quick to respond to this letter. In the same magazine, the US pharmaceutical company has stated that alternative dosing regimens for its vaccine have not yet been evaluated and that the decision to do so rests with the health authorities of each country or continent: “At Pfizer we believe that it is essential that health authorities monitor alternative dosing schedules implemented to ensure that vaccines provide the maximum protection possible ”.

Previously, the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) were shown contrary to prioritizing the first injection and extend the time between both doses. The EMA recommended not to extend the administration of the second dose until 42 days because, although the product information does not specify the time that must pass, “the dosage recommendations make an explicit reference (…) where it is specified, respectively, that the evidence of efficacy is based on a study in which the administration of 2 doses were performed 19 to 42 days apart ”. A) Yes, any changes must be supported by clinical data, “Otherwise, it would be considered ‘off-label use’”.

For its part, the FDA also warned that changing the doses of vaccines can put public health “at risk” and undermine efforts to immunize the population: “It is premature to suggest changes in doses (two for Pfizer and Moderna with 21 and 28 days interval between each dose) or in the programs authorized by the FDA on these vaccines. and these suggestions are not solidly based on the available evidence ”.

The United Kingdom opted for this strategy

Despite the FDA and EMA stance, UK began to follow the strategy proposed by Danuta Skowronski and Gaston De Serres. Thus, since his vaccination campaign began, decided to extend the administration of the second dose to 12 weeks to reach a greater number of citizens with the first. In this way, until last Tuesday 15.57 million doses had already been administered, while that only 546,165 people had received the second injection.