Coronavirus crisis - Between vaccines and natural infections, a balance must be found

How far to rely on vaccines to contain the Covid-19 epidemic? Even if their effectiveness decreases against contamination, doctors point out that their role remains essential. But, in the long term, a question arises: the place to be left to natural immunity.

“We now know that vaccination will not eradicate SARS-CoV-2”, the coronavirus causing Covid-19, acknowledged Wednesday in a press release the French Academy of Medicine, the body supposed to carry the speech discipline in the country.

For several weeks, data have been accumulating to show that vaccines are less effective against the Delta variant of SARS-CoV-2, which is much more contagious.

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A significant proportion of those vaccinated have been infected with the virus, even if they remain very well protected against serious forms. It therefore becomes difficult to envisage collective immunity, that is to say a sufficient threshold of immunized people for the epidemic to stop progressing. However, the Academy of Medicine calls for “not to give up” on this collective immunity.

Because a nuance of size is often misunderstood. Herd immunity does not amount to making the virus disappear completely. The objective is that the number of contaminations remains stable over time or, at least, only experiences regular fluctuations over the seasons.

And it is the vaccination of the greatest number which makes it possible to accelerate this evolution “towards a profile of banal infection with seasonal recrudescence”, according to the Academy. For this, the initial role of vaccines is almost no debate within the scientific community.

But, beyond that, it is less obvious to settle the question of the strategy for the years to come. Should we bet everything on vaccines and multiply reminders to compensate for their loss of effectiveness? “The objective is not to continue to have to vaccinate for eternity”, nuanced the German virologist Christian Drosten at the beginning of September, on the NDR channel.

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Global immunity built by bricks

According to him, no doubt, it is currently necessary to vaccinate as many people as possible, in order to prevent a first encounter with the virus resulting in a serious form of the disease. But, subsequently, we can let infections occur in large numbers among the population, at least when people are not at risk.

In individuals already vaccinated, these contaminations will have little risk of being dangerous, according to the virologist, who is thus counting on a global immunity built by successive bricks (vaccine and natural infection). Christian Drosten, who expresses a personal position here, is based on a crucial notion, that an infection with the virus allows you to be immunized longer and more effectively than if you have been vaccinated.

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At the end of August, a retrospective study carried out on several hundred thousand people in Israel – a country particularly advanced for vaccination – concluded that contaminations were much more frequent among vaccinated people than among those who had already been infected with the virus.

These data – to be taken with caution because they have not yet been independently evaluated – should not, however, suggest that it is better to be infected than to be vaccinated. Some researchers, anxious to avoid interpretations unfavorable to vaccination, therefore point out that we are still far from being able to develop a strategy that leaves room for natural immunity.

“A big playground for the virus”

“It is a situation that could happen but which is not yet for immediately”, nuance with AFP Jean-Claude Manuguerra, virologist at the Pasteur Institute. “We still have a lot of people who are not vaccinated in the world.”

He does not, however, reject the merits of this strategy, provided that care is taken to continue to vaccinate in a targeted manner the people most at risk.

Another element to watch for Jean-Claude Manuguerra: the circulation of the coronavirus in children who, too young to have been vaccinated, can constitute a "big playground for the virus" even if they have only a tiny risk. to develop serious forms themselves.

AFP

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