The cross : Given the current situation, is a fourth dose of vaccine necessary?
Alain Fisher: The question arises, but today there is no element that allows us to decide. In a context where Omicron is less sensitive to vaccination, the question is how long we are protected from this virus with three doses. It is known that three months after the booster, protection against infection decreases, and more with the Pfizer vaccine than with Moderna.
UK data also shows that three months after the booster, protection against hospitalization is still 90% effective. For the months of November and December, we did not observe a significant increase in the number of hospitalizations of people who had a recall. These fragments of information on protection against severe forms are for the moment rather reassuring and today there is no signal suggesting that immunity is crumbling.
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But the information we have is still very incomplete, and we are constantly on the lookout for additional information from France and countries that started recalls earlier than us, such as Israel. In the current state of things, we can have additional information in two weeks or three months. We can also imagine that the immunity will remain stable for a long time, which is not excluded.
Who would be affected by this possible fourth dose?
FA: Already, there are very profoundly immunocompromised people and their entourage, to whom it is reasonable to offer a second booster. This is an instruction that has already existed for a few months and concerns approximately 200,000 people. For the rest of the population, the discussions on this possible second reminder concern people over the age of 65, people with comorbidities and health professionals. For the moment, our reflection does not relate to the whole of the population because there are no elements which encourage us to generalize this booster dose, which in addition could give the signal to the population that it need to be vaccinated often.
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In terms of vaccination priority, the main thing is that the 25% of people over 65 who have not yet received their booster receive their 3e dose, in addition to continuing the first and second doses.
The recall (3e dose) remain mandatory even if you contract Covid-19 after having received two doses of vaccine?
FA: These are the guidelines that apply today, but it is a matter under discussion. This directive is subject to change. The position of the Council for the orientation of the vaccine strategy is as follows: for people who have contracted the virus more than three months after the complete primary vaccination (two doses), this infection is worth a booster shot and it is not necessary to receive a new injection.
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If, on the other hand, this infection occurred less than three months after the primary vaccination, it will not be worth a booster because the interval is insufficient to have the “booster” effect on immune memory, which is classically obtained with a booster. In this case, it would be reasonable to consider doing a booster two or three months after this infection. At this point, that’s just the Council’s view. On the other hand, during the primary vaccination (the administration of the first two doses) one infection is equivalent to one dose.