Technology Covid-19: three to six week delay between the two doses, a crisis strategy

Covid-19: three to six week delay between the two doses, a crisis strategy

A nurse prepares a syringe for vaccination against Covid-19 at the hospital in Châteauroux (Indre). (JÉRÔME COLLIN / FRANCE-BLEU BERRY)

After watching with suspicion our British neighbors extend this period, we finally follow suit, in order to be able to vaccinate more people faster. Forget the strategy of securing the second dose, or taking the time to vaccinate only the most vulnerable, as advocated by HAS! We will manage the vaccine doses delivered on a just-in-time basis.

Normally, at the end of January, we should have vaccinated residents of nursing homes and nursing staff over the age of 50. This represents a little over two million people. According to the vaccine ordering schedule, presented by the government on Thursday, January 7, this is precisely the number of doses that we will have received at that time. Postponing the second injection by a few weeks therefore makes it possible to wait for additional deliveries (provided that the AstraZeneca vaccine is approved in January), while starting to vaccinate people over 75 years old. There, that represents five million people in France.

The first to be concerned about this delay is the manufacturer Pfizer, since it combined its vaccine to be 95% effective with two doses three weeks apart. With one dose, it is only 52% effective. But these tests also showed that ten days after the administration of the first dose, there is already a very protective effect of the vaccine. The second dose mainly helps to make the protection last longer.

The protocol provided for a window between 19 and 42 days to administer the second dose. For the Medicines Agency which gave its opinion on the subject last night, it is therefore that there is no risk in going until this deadline. And she also assumes that the protective antibodies do not abruptly reduce between the 21st day and the 42nd. Like the WHO, she now believes that there may therefore be some flexibility, except for very old people with weaker immune systems.

The agencies recognize this, they concede this flexibility because of the more contagious variants and to compensate for possible shortages. This agitates the scientific sphere: especially when our English neighbors are considering extending the time to three months or even mixing an injection of Pfizer with an AstraZeneca. An act of desperation in the face of the epidemic for some scientists, since it has not been studied in clinical trials.

The United States remains cautious but according to the New York Times, the US National Institute of Health is testing the effectiveness of Moderna’s vaccine with a single dose. A crisis strategy that also shows that after fearing that people will not get vaccinated, governments now fear that there are not enough vaccines for everyone.

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