She was expected. A seventh wave of Covid-19 hits France.
The president of the Scientific Council, Jean-François Delfraissy, estimated, Thursday, June 30, that the epidemic peak linked to this new wave would arrive at the end of July. A noticeably different estimate from the one he had given twelve days earlier, when he was predicting it for “end of June or beginning of July”. As concerns grow over a summer disrupted by this pandemic ebb, franceinfo explains why it is so difficult to predict the peak of this wave.
Because there are no projections for this wave
Samuel Alizon, research director at the CNRS, reminds franceinfo that “no one can predict the future” and that specialists can only elaborate “scenarios to capture the field of possibilities”. He points out that this was done successfully, in France, for the wave linked to the BA.2 sub-variant, which raged in March. But in reality, no scenario has yet been established to date for the new epidemic rise linked to the new BA.4 and BA.5 variants, explains to franceinfo epidemiologist Mircea Sofonea, who works with Samuel Alizon in the ETE team in Montpellier.
“This is the first wave in France for which we have no projection.”
Mircea Sofonea, epidemiologistat franceinfo
This team has been one of the most cutting-edge French research centers since the start of the pandemic. Until recently, ETE regularly published models based on hospital data in order to anticipate the date and height of epidemic peaks of Sars-CoV-2 in France. But this work was not done for this seventh wave. The researchers regret a lack of resources. “I spend a significant part of my time responding to calls for projects simply to obtain the means to do research”regrets Mircea Sofonea, who claims to have suffered several refusals in recent months from organizations such as the National Research Agency, which funds public research in France.
Samuel Alizon also judges that “the main current difficulty” concerning the projections of the seventh wave lies in “the lack of material support for our teams and the disinterest of the authorities”. “Only the Occitanie Region and the University of Montpellier have supported our constant work of projecting hospital needs”says Mircea Sofonea.
The lack of reliable, local and up-to-date data is also blamed. “The last study we have in France on the places and circumstances of contamination, carried out by the team of Arnaud Fontanet at the Institut Pasteur, dates from August 2021. However, since then, the health context – variants, measures and behaviors – changed”alarmed Mircea Sofonea.
For its part, the School of Advanced Studies in Public Health (EHESP) explains to franceinfo “that no projection intended to be made public has been made for the moment” by its epidemiologists. At Inserm, “we are continuing to work on it but at this stage the situation does not allow us to have projections”, recognizes research director Vittoria Colliza with franceinfo. Finally, at the Pasteur Institute, “analysis is in progress” but “they are not published yet”.
Because it is now necessary to consider many parameters
Modeling in epidemiology has never been easy. It was even less so for Covid-19, a disease for which researchers had neither previous data nor hindsight, given its recent emergence, as explained to franceinfo Simon Cauchemez, epidemiologist at the Institut Pasteur, in December 2020.
In the summer of 2022, the situation became even more complex. Even if projections had been made, they would have been more delicate than for the previous waves. Take vaccination coverage, which is generally high in France (78%). It protects the French, assured Jean-François Delfraissy, declaring: “The wave will not ruin the summer because we are vaccinated”. However, in detail, the vaccination rate differs according to age groups or even according to regions. Not to mention that the vaccinated did not receive their injections at the same time, because of the different campaigns, and that the protection conferred by the vaccination dwindles over the months. It is for this reason that Professor Alain Fischer invites those over 60 to get a second vaccination booster (a third or fourth dose depending on the case).
“Epidemiological modeling is generally based on compartmentalisation. At the start of the pandemic, the population was essentially compartmentalised by age, explains Mircea Sofonea. But with vaccination and successive infections, we greatly increase the number of compartments, and at the same time the parametric holes in our models.”
“The epidemic situation has become extremely complex at this stage because of the level of immunity which is very complicated to estimate”, abounds Vittoria Colizza, epidemiologist and director of research at Inserm, because of the different variants, the different vaccines, or even the interactions between infections and vaccination. “The very rapid succession of variants prevents us from having good estimates for these factors in real time to have robust and reliable projections”, she concludes.
Because the BA.4 and BA.5 sub-variants slip through the cracks
If vaccines are still our best weapon in the face of the pandemic, their effectiveness against new sub-variants (BA.4, and especially BA.5) is weakened. “It seems that these variants spread more quickly (…) because they escape more immunity acquired by vaccination as by infection”noted to franceinfo Samuel Alizon. “People who have a complete regimen are very well protected against severe formstempered epidemiologist Antoine Flahault on franceinfo. They’re not protected from having Covid, unfortunately, because it’s not exactly the same strain anymore.”
>> Covid-19: what we know about the BA.5 sub-variant, which is more contagious and which will become the majority in France
Public Health France underlines in an analysis of June 15 (PDF) that the BA.5 subvariant is not the only factor to have a “major impact” in the ongoing epidemic recovery. The health agency also points “the decrease in adherence to barrier measures” and “the increase in the number of contacts”.
Because it is difficult to compare with other countries
In an attempt to anticipate events despite everything, specialists are scrutinizing the situation elsewhere, particularly in Portugal. In previous rebounds, he had been hit a few weeks before France. This is once again the case for this seventh wave. The epidemic rebound, caused by the new BA.4 and BA.5 variants, started in early May in Lisbon and the peak of contamination was reached in early June. Considering that France is six weeks apart, with a rise in cases that began in mid-June, some epidemiologists, questioned in particular by Le Figaroare betting on a peak reached at the end of July.
Other researchers qualify this comparison. Arnaud Fontanet, of the Institut Pasteur, told the regional daily West France that the situation was “a little different”, between France and Portugal. The epidemiologist notably noted the fact that the BA.2 wave which hit France in the spring was less strong in Portugal. The Portuguese population could therefore have been less protected against BA.5 which is quite close to BA.2.