In Manaus in Brazil, the new epidemic outbreak - probably caused by the Brazilian variant - is such that it is up to families to provide oxygen cylinders to treat sick relatives.
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NEW CHINA / SIPA
Among the new variants of the coronavirus that have emerged, the strain currently circulating in central Brazil could affect the immune response.
This Brazilian variant could thus be responsible for a large number of cases of re-infections with Covid-19.
And it raises the question of its effect on vaccination, which is gradually starting on the planet.
P.1.
A letter and a number to name this Brazilian variant which sows chaos in Manaus.
This Brazilian city of 2.2 million inhabitants, located in the heart of the Amazon rainforest, is currently undergoing a deadly new wave of the coronavirus epidemic.
Explosions of contaminations, saturated and even completely overwhelmed hospitals, multiplication of deaths ... Since December 2020, Manaus no longer sinks under a wave but under an epidemic "tsunami", and buries more than a thousand of its inhabitants every day.
How to explain this new outbreak?
And is it possible to stop the spread of this variant?
A variant responsible for the Manaus epidemic outbreak
The Brazilian state of Amazonas, of which Manaus is the capital, had already suffered a very severe first wave in April 2020. It was there that the images were shot of giant cemeteries hastily dug to bury the thousands. deaths caused by the virus.
The spread of the virus has been such that the majority of residents have contracted Covid-19.
A recent study published in the journal
Science
has
thus demonstrated that in the fall, more than three quarters (76%) of the inhabitants had developed antibodies against SARS-CoV-2.
A figure that should logically have allowed the city to be protected by collective immunity.
However, from mid-December, Manaus was therefore again faced with an outbreak, forcing residents to obtain oxygen cylinders themselves to treat their sick relatives.
"It was difficult to reconcile these two elements," said Nuno Faria, virologist at Imperial College London, professor at the University of Oxford and co-author of the study published in
Science
.
The virologist then seeks to know if a mutation of the virus could be the cause, thanks to the sequencing of several samples.
The P.1, or Brazilian variant, is thus identified in thirteen RT-PRC samples out of thirty-one sample collected between December 15 and 23, while it did not appear in sequenced samples collected between March and November 2020.
And like the English and South African variants, this Brazilian variant unearthed in December could be much more contagious and explain this epidemic resumption in Manaus, where, in recent days, the death rate linked to the virus has increased from 142 to 187 per 100,000 inhabitants, almost twice the national average.
"This is the most plausible explanation for such explosive growth," said Jesem Orellana, researcher at the Fiocruz Amazonia institute, to the newspaper
Estadao de Sao Paulo
.
But "it is too easy to blame the variants and say that it is the virus which is responsible", tempered during a press briefing on January 14 Mike Ryan, epidemiologist at the World Health Organization (WHO), pointing to the slackening of the local population while respecting barrier gestures.
A mutation that affects the immune response
But if this epidemic rebound in Manaus is indeed attributable to P.1, by what mechanisms did this variant act?
Nuno Faria and other researchers from Imperial College London and the universities of Oxford and São Paulo unveiled its characteristics in an article published Jan. 12 on virological.org.
This P.1, which descends from a strain that has already been widely circulated in Brazil, has the particularity of containing a wide range of mutations.
And one of them, the E484K mutation, would have unfortunate effects on immunity.
This mutation is "the most worrying of all" in terms of the immune response, said Ravi Gupta, professor of microbiology at the University of Cambridge.
Laboratory tests have shown that E484K seems capable of reducing the recognition of the virus by antibodies, and therefore its neutralization.
"As such, it can help the virus bypass the immune protection conferred by a previous infection", explains Professor François Balloux, of University College London.
And this is precisely what a study published on January 6 reports, which describes the case of a Brazilian woman infected with Covid-19 in May 2020, then reinfected in October by a variant carrying this E484K mutation.
A more severe reinfection than the first, which would be a sign that the mutation caused a poorer immune response in the patient.
The collective immunity achieved by the first wave in Manaus could therefore no longer be effective enough to prevent contamination by this new variant.
The efficacy of the vaccine affected by the variant?
To date, Brazil is one of the nations most affected by the pandemic, with nearly 210,000 dead.
Caught in a race against time, the country launched its vaccination campaign on Monday.
The government of Jair Bolsonaro is betting on the Chinese vaccine CoronaVac, one of the two authorized on January 17 by the Brazilian regulator, with the Briton AstraZeneca.
But if the immunity conferred by a primary infection with Covid-19 does not protect against reinfection with the Brazilian variant, will the same be true for the immunity induced by the vaccine?
A prospect of "immune escape" which worries scientists.
On January 8, the Pfizer-BioNTech duo assured that their vaccine was effective against the N501Y mutation, present in the English variant.
But their lab checks did not focus on the E484K mutation.
They are therefore not sufficient to conclude that the efficacy of the vaccine will be the same against the Brazilian variant.
However, there is no indication that the E484K mutation is sufficient to make variants resistant to current vaccines, scientists say.
“Even if you decrease in efficiency, you will normally still have neutralization of the virus,” says Vincent Enouf, of the National Reference Center for Respiratory Viruses at the Institut Pasteur, in Paris.
"I do not think that this mutation alone is problematic for vaccines," added immunologist Rino Rappuoli, researcher and scientific manager of pharmaceutical giant GSK.
In the meantime, in Europe, the United Kingdom and Italy have decided to close their borders to people arriving from Brazil.
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