SCIENCE – Another victory for Pasteur? In their latest models, the teams of the famous French institute estimated that the peak of cases of the fifth wave of coronavirus, carried by the Omicron variant, would be reached in mid-January.
And if we must not declare victory too quickly, the figures for the monitoring indicators of the Covid-19 clearly seem to be going in the direction of the projections of the Pasteur Institute in recent days. Be careful though: if a peak emerges, it will be necessary to wait several days to ensure that the trend is indeed the right one.
And if this is the case, it will also be necessary to check whether the hospital indicators are indeed following the same trajectory with a ten-day lag. Finally, it remains to verify the rate of decline of the epidemic.
To fully understand where France is today in the face of Covid-19, The HuffPost invite you to watch the last digits, but especially their evolution in maps and curves. An important point to keep in mind before continuing your reading: the data is always published in the evening. Thus, the updated figures for this Saturday January 15 are those published the day before, Friday 14.
You should also know that these are not the figures for the day, but those on D-1 for the number of hospitalizations and the number of new confirmed cases. For the incidence and the positivity rate, the D-3 screening figures (on the date of the test) are used.
National Covid-19 curves
Friday, January 14, the Directorate General for Health has identified 329,371 positive cases, a figure equivalent to that of the previous Friday, when there were 328,214 cases. If we look at the average evolution (over 7 days, the blue curve), we see that the fifth wave, swollen by contamination linked to the Omicron variant, seems to be marking time. However, we must remain very cautious as long as the trend is not confirmed over several days.
The figures on D-1 are practical for monitoring the evolution of the epidemic as closely as possible, but are likely to vary from one week to another depending on the speed of feedback of the results. To be sure of the trends, it is best to look at the data published by Santé Publique France, which shows the number of cases on the date of screening, with a delay of three days.
The first graph below shows the share of the Omicron variant and the Delta variant in the positive cases. As you can see, Omicron has taken hold, but Delta has not completely disappeared and continues to drive tens of thousands of cases every day.
The graphs below show the incidence, as well as other essential indicators to follow the evolution of the epidemic. We see for example that new hospitalizations are climbing again at a significant rate, as the peak of the third wave is exceeded. The positivity rate is approaching 20% for the first time.
Meaning of the different indicators
- Incidence rate: this is the number of cases detected per 100,000 inhabitants. It is very useful, because it gives an inventory of the epidemic in almost real time (a few days lag for the appearance of symptoms, or even before their appearance for contact cases). But it is dependent on screening capabilities.
- Positivity rate: this is the number of positive tests compared to the total tests carried out. It makes it possible to “control” the incidence rate. If there are many cases in a territory (incidence rate), but this is only due to very developed screening, the positivity rate will be low. Conversely, if it increases, this means that a larger proportion of people tested are positive, but above all that the infected people who are not tested, who fall through the cracks, are potentially more numerous.
- Occupancy rate of intensive care beds by Covid-19 patients: It is a scrutinized figure, because it allows to know if the hospitals are able to manage the influx of patients. It is very useful, because there is little risk of bias: it does not depend on screening and bed occupancy is well reported to the authorities. Its disadvantage: there is a significant delay between the contamination and the passage in intensive care, of approximately two to three weeks.
- Intensive care admissions and new hospitalizations: smoothed average over 7 days of people entering the hospital
- Death in hospital: Like revives, it is a rather reliable indicator, but with a significant delay.
- R effective: this indicator represents the actual “virus reproduction rate”, i.e. the number of people infected by a contagious case. It is calculated by epidemiologists and also has a significant delay.
For the first time since November, the incidence rate has been falling very slightly for two days. It went from 2843 to 2829. This start of the trend could herald the peak in cases hoped for by the Institut Pasteur, but we must remain cautious and wait for several days of decline. Similarly, intensive care admissions have been stagnating for a few days. At the same time, new hospitalizations continue to climb.
Above all, it will be necessary to check the rate of decline of the cases, and then, hopefully, of the hospital indicators. For this, it is interesting to look at the evolution over a week, in percentage, of these figures:
Here, we also see a trend: if, over a week, all the indicators are still on the rise (the bars are climbing upwards), growth is losing speed. The increase in incidence over one week is now only 25% against 130% at the beginning of January.
It is only once the purple bars are down that we can say that the peak of this 5th (or 6th) wave will truly be reached (provided this decline lasts).
The Omicron variant changes the shape of the wave
As incidence and positivity have soared, why aren’t hospital indicators in the bright red? Again, because the Omicron variant is a game changer, with its lesser severity. It is difficult to know to what extent this drop in virulence is linked to its mutations or to the fact that it infects vaccinated people, and therefore strongly protected against serious forms.
Still, the dropout between cases and hospitalizations or resuscitation is flagrant. The graph below shows the evolution of the number of cases, hospitalizations and intensive care admissions in percentage compared to the highest reached during the second wave of Covid-19, in November 2020.
Before the arrival of this new variant, the highest number of cases had been reached in early November 2020, for the second wave. For hospital indicators, the peak took place at the beginning of April 2020, at the time of the first wave.
As we can see, the difference between cases and hospitalizations or intensive care admissions is obvious with Omicron. Before that, lighter divergences are visible between the waves. They are difficult to explain with certainty, but several tracks can be evoked: the severity Alpha and Delta variants, the evolution of the vaccine campaign, etc.
The map and graph below show the dominance of Omicron throughout the country. Even if some regions are more affected than others, the variant represents more than 85% of positive cases in all regions and up to 97% in Île-de-France.
Map of the incidence rate by department
If we look at the evolution of the epidemic in a more local way, we see that the trend is still on the rise, but that the growth in incidence is increasingly weak in many departments, as can be seen on the map below which shows the evolution of the incidence rate over a week.
It should be remembered that in metropolitan France, all departments are at unprecedented levels of incidence, with the 1000 mark exceeded everywhere. The threshold of 3000, if not 4000, has even been reached in many departments.
The graph below allows you to analyze the situation in your department in more detail.
The intensive care occupancy rate map
As for hospital indicators, the occupancy rate in intensive care is now above 50% in all regions. The tension is very clear in Paca and Corsica where there are more patients than places normally available. Transfers of patients have already taken place.
A very effective vaccination, but which skates
How to explain this fifth wave? It is difficult to say as the coronavirus has managed to thwart our forecasts, but it should already be remembered that an increase was foreseeable from the beginning of autumn with the dominance of the Delta variant, which is much more contagious. Since then, the Omicron variant has come to play spoilsport.
A controlled rise in the epidemic in the middle of winter, with limited measures (such as the health pass, the wearing of a mask, the ventilation of closed places, etc.), was only possible thanks to vaccination. If the vaccine does not provide 100% protection, it reduces the risk of infection and drastically lowers the risk of developing a severe form of Covid-19.
Today, 78% of the population is doubly vaccinated, as can be seen in the graph below, with disparities between age groups.
But we now know that the effectiveness of the vaccine against the infection decreases over time, especially six months after vaccination, and even more so with the Omicron variant. Protection against severe forms of Covid-19 remains high, but still seems to be decreasing, especially among the elderly.
This is why many countries, including France, have launched a recall campaign. In his forecasts from the end of November, the Institut Pasteur estimates that a booster dose, by further reducing the risk of hospitalization of those most at risk and by reducing the risk of being infected, can theoretically lower the peak of hospitalizations . Thus, a reminder for the over 65s reduces the height of the peak by 20%, while a reminder for all adults causes it to fall by 44%.
The fulgurance of the Omicron variant makes this third dose even more essential, about 43% of the population has already received it.
Vaccines still effective against Covid-19
The effectiveness of vaccines and of the third dose is easily seen if we analyze the number of vaccinated or non-vaccinated positive people, hospitalized or in intensive care.
On the other hand, we must be careful: more than 91% of adults are vaccinated. It is therefore logical that there are many vaccinated people in hospitals. But if we compare with equal numbers (how many hospitalized for a million vaccinated, versus how many hospitalized for a million non-vaccinated), we can see that the vaccine is very effective.
The proof with the graphs below. We also see that the booster increases the effectiveness of the vaccine even more.
See also on The HuffPost: After Omicron, what will be the future variants?