Should we recommend a single injection for people who have already been contaminated with SARS-CoV-2 and therefore have a priori antibodies?
At a time when France is lacking doses of vaccine, the question has come back to the fore in recent days thanks to the publication of two American studies, suggesting that a single dose could be enough.
This would also make it possible not to draw too much into just-in-time stocks.
At the end of December, the High Authority for Health had already been seized of the question of whether people infected in the past should be vaccinated.
This potentially concerns the more than 3 million citizens who have tested positive in the past year.
“At this stage”, the agency considered that there was “no need to systematically vaccinate people who have already developed a symptomatic form of Covid-19”.
However, these former patients must be able to be vaccinated if they wish after a decision shared with their doctor, she said.
The bites must then occur at least three months after the onset of symptoms but it was not indicated that a single injection would be sufficient, meaning that two would be needed.
Two promising American studies
The HAS tells us that it is preparing to issue a new opinion on the subject "in the days to come", without revealing anything of its content.
Several interlocutors expect the recommendation to be for a single injection instead of two (for people who wish to be vaccinated), at least three or six months after infection.
"In view of the data in the scientific literature, the opinion should go in this direction", judges immunologist Stéphane Paul, member of the Vaccine Covid committee.
"I think likely that only one injection will be recommended, not for a question of availability of vaccines but simply for a question of strategy", adds another actor of the file, which looked at the two American studies.
These, which are only at the pre-publication stage, do indeed seem promising.
One of them showed that people infected in the past had generated at least as many antibodies after a single injection of mRNA vaccine (Pfizer / BioNTech or Moderna) as the others with two doses.
"I think one vaccination should be enough," senior author Florian Krammer, a virologist at Icahn School of Medicine at Mount Sinai, New York, told The New York Times.
So, here is our data comparing immune responses in people who had a SARS-CoV-2 infection and were then vaccinated once and people who were naive and then were vaccinated once.
I'll explain this a little better tonight if I find time.
https://t.co/6EOEZq8tod
- Florian Krammer (@florian_krammer) February 1, 2021
These two studies, however, relate to very small samples, respectively 109 and 59 people.
"It is obvious that it would be better to have studies carried out on more people but the urgency is there, we must therefore issue a recommendation in the current state of knowledge which seems to show that a single dose would be sufficient to achieve a high level of antibodies, ”Judge Stéphane Paul.
"These two recent studies show that it would be quite relevant to recommend only one dose", adds Jean-Daniel Lelièvre, head of the immunology and infectious diseases department at Henri-Mondor hospital (Créteil).
The unknown duration of immunity
In addition, one of the two American studies suggests that people already infected would have more side effects such as fatigue, headache, chills, fever and muscle pain after the first injection.
It may be the same - or even worse - with a second dose.
"I spoke a little bit with fellow infectious disease specialists who advised me to take a first dose," Remi Salomon told France Info on Tuesday, chairman of the AP-HP establishment medical commission (Public Assistance -Hospitals of Paris) and contaminated last March.
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However, some questions remain unanswered.
What about the duration of immunity with a single dose of vaccine, for example?
“For a person who receives two doses, we start to accumulate data over eight or nine months showing good protection.
But someone who had the Covid six months earlier and who is injected with a single dose, we do not yet have a very precise idea of the duration of immunity, ”admits Stéphane Paul, who does not exclude not that the recommendations can change over the next few months.
The entourage of careful Olivier Véran
It will also be necessary to establish whether the same rule can apply for all types of vaccine and to everyone.
A person who tested positive but asymptomatic at the very beginning of the pandemic, a year ago, does not necessarily have the same level of antibodies today as another seriously affected person only three or six months ago.
"It is much easier to set a general framework, even if it is true that the question may arise for people with immunosuppression, for example", indicates our actor at the heart of the matter.
Eleanor Riley, professor of immunology and infectious diseases at the University of Edinburgh, also considers "logistically complex" to capitalize on this strategy as part of a "mass vaccination".
“It may be safer, overall, to make sure everyone gets two doses,” she told the British Medical Journal.
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For its part, the entourage of Olivier Véran believes with the Parisian not "have the necessary hindsight" to change the strategy in force at this stage.
Responsibility for "health authorities to gather information and then issue recommendations".
Which is therefore, a priori, only a matter of days.