Covid-19: how effective are vaccines against variants?
Vaccination center in Tel Aviv, February 9, 2021. AP - Ariel Schalit
Text by: Simon Rozé Follow
4 min
Israel is the most advanced country in the world in its vaccination campaign against Covid-19.
The effects are starting to be felt in the country, despite the presence there of the British variant.
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Almost two-thirds of the Israeli population has received at least one dose of the vaccine.
Among them, 9 out of 10 people over the age of 60, 80% of whom even received the two necessary doses.
An
article from
Nature
taking up a study by the Israeli Ministry of Health, shows that the first effects are being felt: the curves of new cases and hospitalizations have started to decrease.
However, it must be ensured that this is not an effect of the third confinement in force in the country.
This does not seem to be the case: if we look by age group, we notice that the curve of the elderly, highly vaccinated, decreases much faster than that of the youngest.
If this was due to containment, they would have decreased at the same rate.
Vaccination therefore seems to show its effects.
There was, however, concern in Israel, as this decrease was expected earlier.
This is because the vaccination campaign coincided with a surge in cases, notably caused by the emergence of the more contagious British variant in the country.
However, this did not have a priori impact on the efficacy of the vaccines used in Israel, in particular that of Pfizer / BioNtech based on messenger RNA.
Different variants, different vaccines
Indeed, the question of its effectiveness and that of other vaccines arises in the face of the British, South African and Brazilian variants.
The answer will not be the same depending on the variant and the vaccine used, as their technology differs.
"
Vaccines of the messenger RNA type and recombinant viral vectors induce a very important immune response
," explains Brigitte Autran, professor of immunology at the Sorbonne University faculty of medicine.
It is made up of both antibodies and killer cells capable of destroying infected cells.
Inactivated vaccines will essentially induce antibodies and not killer cells.
These differences are not only technical, they have a consequence on the effectiveness of vaccines, especially in the face of variants.
For the Briton, the first data are reassuring, and the current vaccines seem sufficient.
However, the concern is more present for the South African and Brazilian variants, which carry the
same problematic mutation: E484K
.
The data from the clinical trial of the vaccine developed by Novavax illustrate this challenge: “
It has given excellent protection results in England, in the order of 90%.
In contrast, it was only around 50% in South Africa.
However, this vaccine essentially induces an antibody-based response, and few killer cells.
We can therefore still hope that messenger RNA type vaccines retain greater efficacy on this variant,
”Brigitte Autran analyzes.
Hope in the laboratory
Laboratory work supports this hypothesis.
Also in
Nature
, a team from the University of Texas is publishing results obtained
in vitro
on the effect of Pfizer's vaccine against the South African variant, and in particular on the E484K mutation.
The observed efficiency is certainly lower, but it is still present at a level deemed satisfactory.
As always with work carried out in the laboratory, these however require confirmation in the field.
Finally, in addition to the strong immune response they induce, messenger RNA vaccines have another great advantage: this technology allows them to be quickly updated to cope with the emergence of variants, if they become dominant.
It is only the process of industrialization and distribution that will limit their availability.
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Read also: Covid-19: promising results for the treatment of Eli Lilly and other scientific news
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