Can French hospitals cope with a new epidemic wave of SARS-CoV-2?

EXPERTS OPINION – Researchers Samuel Alizon and Mircea Sofonea are looking to Le Figaro on the risks that a new outbreak would pose to the hospital, and the means to protect oneself from them.

At the start of 2020, the first epidemic wave took the country by surprise. The estimates of our models at the time, refined since by precise geographic simulation approaches, indicate that if no braking measure had been adopted, the wave would have infected more than one in two people in France; or in one year more than 240,000 deaths in hospital and at least double the number of hospitalizations, given the lethality of the infection and the national age pyramid; figures consistent with the tragedy experienced by the city of Manaus, Brazil, in 2020.

The second and third waves of epidemics were announced by scientists in August 2020 and at the end of January 2021. But the minimization of the risk of their occurrence by the authorities, combined with their low reactivity, left no alternative to strict confinement because the natural immunity then vaccination of the population was clearly not enough to prevent an overwhelming of critical care services.

“It is dangerous to rule out the risk of hospital pressure (at least local) in metropolitan France after the start of the school year, simply because of” higher “vaccination coverage”

Samuel Alizon and Mircea Sofonea

What about the fourth wave, the premises of which have been studied from June 18 by our team?

The sharp deterioration in the health situation experienced by Martinique and Guadeloupe has put the contagiousness of the Delta variant twice as high on the media scene compared to lines circulating in early 2020. British data also suggest a higher virulence with increased risk of hospitalization. Admittedly, vaccination coverage in the West Indies is low and the previous epidemic waves were of limited magnitude there, and the population is therefore not very immune. However, it is dangerous to rule out the risk of hospital pressure (at least local) in metropolitan France after the start of the school year, simply because of “higher” vaccination coverage. More quantitative reasoning is needed, and modeling can make an original contribution to the necessary public debate.

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Let us recall the obvious: it is very difficult to anticipate the epidemic dynamic beyond five weeks for the simple reason that it can be influenced by political choices and changes in behavior. The application in France of a logic of pro-active control of the epidemic or, conversely, a general relaxation of prevention measures as we have seen in Brazil or India, would lead in one month to tendencies the opposite of each other. On the other hand, we can estimate the impact of an epidemic wave of a given size in France from the proportions of people immunized (by vaccination or infection) and the risks of hospitalization associated with an infection, assuming a uniform surge. of the wave on the population. All these quantities are obviously to be corrected according to the ages. This is what our COVimpact software does for France at the departmental, regional and national level.

Currently, 3 in 4 adults have received two doses of the vaccine in France and more than 90% of people aged 70 to 80 are vaccinated. Although vaccines are very effective in preventing severe forms of the disease (reduction by a factor of 10), several real-life estimates suggest that they are more limited in preventing infection (reduction by a factor of 2). In addition, infected vaccinated people, although they very rarely develop severe forms, are likely contagious. In other words, vaccination coverage is not enough to completely prevent the circulation of the virus and therefore, in the absence of braking measures, an epidemic wave. Therefore, the question that arises is whether the (high) protection against severe forms makes it possible to limit the extent of the hospital wave.

SEE AS ​​WELL – Without vaccination, “the fourth wave could have been the worst wave we have known”, explains Véran

4,500 intensive care beds per day

Consider an uninterrupted epidemic wave (therefore without an additional preventive response) with a reproduction number (number of people infected on average by one infected) of 1.15 (at the present time it is lower, but it is a consistent figure with the increase in physical interactions that had been observed at the start of the 2020 school year). According to the simplest models, which capture the situation in large urban centers relatively well, the wave would affect about one in 4 people and last about two months (with an epidemic peak in the first month). With 95% of adults 95% protected against severe forms, this wave would cause around 10,000 ICU admissions. On the other hand, if protection against severe forms is “only” 85%, this figure doubles with around 20,000 admissions; difficult in the current state for hospital services to absorb such a wave in less than 2 months, because this would correspond to approximately 280,000 days of intensive care beds, ie more than 4,500 beds per day on average. These national estimates obviously hide large territorial and temporal inequalities which would probably create saturation locally. To this must be added the current context, with a staff of critical care services tested by a year and a half of mobilization and the difficulty of accepting that a preventable disease cuts into the management of other pathologies.

“Our hospital system, due to its size, resources and exhaustion, does not seem able to cope with a potential large-scale epidemic wave in a short period of time. “

Samuel Alizon and Mircea Sofonea

In summary, given the current immunity in the French population, our hospital system, by virtue of its size, resources and exhaustion, does not seem able to cope with a potential large-scale epidemic wave over a period of reduced time. Obviously, to arrive at this observation, many simplifications are necessary, but most of them tend not to exaggerate the risk. Thus, the average estimate of service demand neglects temporal variations such as a pronounced epidemic peak after one month which would worsen the situation locally. In addition, these calculations ignore the impact of other epidemics of respiratory diseases, such as influenza, which have been limited for more than a year with the barrier measures.

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Faced with this observation, several options, which have varying consequences for the population, make it possible to reduce hospital pressure:

1) Prevention. It is the poor relation of French health policy. Between managing the risk of transmission indoors and following up on contacts, there has been a lot of delay due to the lack of investment. The “test / trace / isolate” policy also sorely lacks the means for tracing and isolation. More generally, the monitoring of the epidemic in France is limited with an underexploitation of sequencing data, PCR test data and an absence of random screening.

2) The spreading of the wave. As noted above, the period of time in which the epidemic wave breaks is an issue. Spreading it over twice as long would lower hospital pressure. But exponential growth is hardly flattened without strong restrictive measures, as the implementation of the 6 p.m. curfew in 2021 has shown.

3) Increase hospital capacity. This option was futile as long as the proportion of the immunized population was not sufficient, because with intensive care admissions doubling every week, doubling hospital capacity only saves one week. But in an immune population, it is an option to consider if it allows “to let through” epidemic waves affecting a quarter of the population. It would nonetheless remain associated with a significant health cost comparable to influenza.

4) Put in place curfews and / or containments. Highly costly socio-economically, academically and culturally, this is the option favored in the past by the authorities, who in October 2020 and May 2021 waited until hospital services were on the verge of collapse to impose these measures. extremes. Its only advantage is at the political level, because the measure appears inevitable when it is put in place.

5) Increase immunity. For this, it is still possible to improve vaccination coverage. However, the main lever in this perspective would be the generalization of a 3e dose of vaccine, but it raises major ethical questions with an explosion of health inequalities at the global level. In addition, its real-life benefits are still uncertain. In practice, such a vaccine booster is unlikely by the fall.

6) Focus on research. This lever is probably the most useful in the long term, but the national investment in scientific research on the prevention and treatment of Covid-19 does not seem to match our country’s ambitions. According to the Global Health Center in Geneva, France is not even among the top 15 nations in terms of funding for vaccine research, the vast majority of which is public funding.

“No model can predict where the COVID-19 epidemic will be by the end of the year, but in the current situation the risks associated with massive and uncontrolled circulation of the virus appear serious. “

Samuel Alizon and Mircea Sofonea

No model can predict where the COVID-19 epidemic will be by the end of the year, but in the current situation the risks associated with massive and uncontrolled circulation of the virus appear serious. On the eve of this new school and professional year, the daily number of tests for SARS-CoV-2 infections is decreasing and we have all the cards in hand to avoid a new crisis. More than ever, it is important to invest in prevention in public health, because the health, economic and democratic cost generated by the wait-and-see policy is beyond measure.

Samuel Alizon is Research Director at CNRS and author of Pandemics, Ecology and Evolution (2020, Points).

Mircea T Sofonea is a lecturer in epidemiology and evolution of infectious diseases at the University of Montpellier


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