"There is no reason not to vaccinate people who have already had covid-19, because vaccination gives a much more robust and lasting immunity than the disease," Muller explains. The European covid digital green certificate will come into force on 1 July--but could see the light of day in Luxembourg by mid-June-- and will in fact be based on three things: proof of vaccination, a negative PCR test less than 72 hours old and evidence of the presence of antibodies following infection.

"If, for example, we have had a mildly aggressive, or even almost asymptomatic, form of the disease, the immunity is quite low," Muller adds. “Conversely, if a person has had a severe form, there has been more virus, which causes the immune system to activate more and produce more antibodies. But the question is, how long do these antibodies remain? And at the moment, we do not yet have a clear answer on the subject. Those who have a lot of antibodies are afraid of getting the vaccine for fear of disrupting their acquired immunity. But this is not the case, on the contrary, they still need to be vaccinated to be protected in the long term."

A third “necessary” dose

Some countries, like France--which followed a recommendation from the high health authority--have decided that when a person has contracted the coronavirus and has antibodies, a single dose of the vaccine is enough to be sufficiently protected. The Belgian health authorities have chosen to administer two vaccine doses (of a double-dose vaccine) in this case.

Regarding Luxembourg, in a parliamentary response dated 12 May, health minister Paulette Lenert (LSAP) explained that the question on the subject had not yet been clarified. For Muller, “even if we have contracted covid-19, we must have both doses of the vaccine, it is more effective. And getting just one dose is also an administrative problem, because in the eyes of the state and the European Union you are not fully immunised."

What about a third dose of the vaccine? “We have noticed that in order to fight the variants, it is important to do the third dose, even if it is not suitable for the variant. If someone has received two doses and has a choice of a third dose, they should take it. And there is no problem if a person has been vaccinated, the first two doses with one vaccine and the third with another, on the contrary. From an immunological standpoint, taking a dose of an adenovirus vaccine like AstraZeneca and then a dose of an mRNA vaccine like Pfizer-BioNTech or Moderna is a combination that works very well. But I think you have to allow a little time to pass between the second and the third dose, maybe a year," Muller says.

This article was originally published in Paperjam and has been translated and edited for Delano.