Simon Cochems (Pasteur):

Scientific articles to put the points back on i. The Pasteur Institute’s team of designers, led by Simon Cochems, who is also a member of the Scientific Council, has published two posts online to answer some of the misconceptions that have sparked public debate in recent weeks. First of all, the fact that vaccination will allow us to resume normal life. This researcher explains that it is possible, but only on the condition that 90% of adults are protected. Otherwise, if such a rate is not reached, its models show that it will either continue to live with the restrictions, or will also immunize children. While his work, in particular, has come under fire in recent weeks – we remember Emmanuel Macron’s directing of “The Explosion of Issues That Was Expected in February” – Simon Cochems also posted a note last weekend explaining her methods, to show their limitations and contributions. Interview.

Can we hope to drop the barrier measures and return to normality soon – if not in the next few months, at least in the fall?

Everything will depend on the vaccination coverage. Unfortunately, it seems difficult to achieve the necessary vaccination rates for the virus to not spread at all by the beginning of the school year. So we took the question another way: How do we prevent a new wave in the fall from surpassing 1,000 hospitalizations per day at its peak? It will definitely be an important level, but it’s much easier to manage than we know so far. However, we believe that up to this goal will require widespread deployment of vaccines. With the virus spreading last year, protecting 75% of adults had loosened restrictions altogether. But with the British alternative, which is much more contagious, Our models show that more than 90% of adults will need to be vaccinated To contain the epidemic while removing all barrier measures.

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The most recent opinion polls indicate that 46% of the French are still hostile to vaccination. So we’re far from the mark …

This level of immunization coverage could correspond to a scenario in which 90% of those over the age of 65, but not children, are protected, and only 50% of those between the ages of 18 and 64 are protected. In this case, if we were to ease all health measures, there would still be a high possibility of contamination with the virus, which would again have a strong impact on our health system. Even in theory, the new wave could be better than the previous waves. But of course we won’t get there, because new curbing measures will be put in place to slow down the pollution.

“If many of us are not vaccinated, we will have to continue to live with the limitations.”

Is it realistic to hope to exceed these levels of vaccination coverage?

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The dose of dose delivery will accelerate. On the other hand, I am not a specialist in accusing the population of vaccination campaigns. The goal of our work is specifically to make the largest number aware that if many of us are not vaccinated, including among the youngest, we will have to continue to live with limitations.

Why do we need such high adult immunization coverage?

This is a good question because in theory, herd immunity should be achieved more quickly. the problem Highlighted by the models Is that if we vaccinate only adults, we would expect a major epidemic in children, even if the vaccination coverage is very high in adults. Therefore, the spread of the virus in children will facilitate transmission of the infection to parents and grandparents who were not vaccinated, or who are not adequately protected with vaccines, because they are not 100% effective.

For herd immunity to fully play its role, we must not only look at the total percentage of the population that has been vaccinated, but we must also make sure that we do not allow the virus to spread to the group of individuals (here the children) who will then pass. On a larger scale in the community.

If children could be vaccinated, our model indicates that we would have to cover 69% of 0-64 and 90% of those over 65 years of age to dispense with any control measures. In the absence of proven injections in children under 18 years of age, the issue of vaccination of children remains theoretical for the time being, but it is important to raise it.

Why isn’t a high level of protection for the most vulnerable – 90% of those over 65 in your example – enough to pull us out of the hardships we face?

Remember the first wave. Barely 5% of the French have contracted the infection, and this percentage was lower among the most vulnerable groups. However, the healthcare system is saturated. If we vaccinate 90% of the most vulnerable, then 10% of that population would still be at risk, which would be enough to overwhelm our hospitals once again in a very sensitive situation once the virus continues to spread massively in the population. Not to mention that with this new variant, even the smallest of them can also find themselves injured and hospitalized, as we see now. Since we now know that vaccination reduces transmission of the virus, it is important that the largest possible number of the population be vaccinated.

In the absence of a great commitment to vaccination, we are not ready to remove the masks, even at the beginning of the school year …

Even with a voluntary level of vaccination by the end of summer – say 90% of older adults, 70% from 18-64 years old – the viral circulation will still matter. This equates to coverage of the population, including children, of only 59%. The virus will then retain a large playing field, and under these circumstances, maintaining a certain level of restrictions will still be essential. It is estimated that transmission rates should be reduced by 15% to 27% compared to the scenario without control measures. It is an effort that remains, however, much less than what we have witnessed recently. For example, lockdowns for 2020 lowered transmission rates from 70% to 80%. We did not seek to evaluate the most appropriate measures – testing – tracking – only isolation, masks, social distancing …

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“There is a kind of cognitive bias that leads us to say that, last summer it was calm, it will be the following summer too.”

Under these circumstances, can we say, as European Commissioner Thierry Breton said, that collective immunity will be achieved in July?

We’ll see where we will be this summer. What our work and that of other modeling groups show is that it takes great ambition and success in achieving high levels of immunization to prevent the spread of the virus. Even if no new variants emerge, we will likely continue to monitor some viral circulation in the fall, with the effect on the health system, even if this is not the same as what we have been through.

Until then, what kind of summer can we expect? Will he be as comfortable as before?

There is a kind of cognitive bias that leads us to say that, last summer it was calm, it will be the following summer too. But this will not necessarily be the case. In the past year, spring’s strict containment has resulted in a very low level of viral circulation. And then this progressed all summer long, without us noticing because we were starting from a very low level. Now, great braking measures have been taken and vaccination has begun, but the virus is also more transmissible. The whole question is knowing to what level of daily pollution all of these factors will lead us at the start of summer. If we stay on a high plateau, even a small acceleration in the propulsion system during the summer period can put us in a difficult position. But of course, by that time, vaccination will also have progressed a lot … We will be able to better assess the situation once we have enough perspective to assess the impact of the restraint measures that have been implemented recently.

In fact, your models have been criticized, starting with President Emmanuel Macron himself, who, speaking of your work, stated, “The explosion of cases announced for the month of February, which finally did not happen.” what about ?

We have just posted a note explaining our approach It shows how we operate. At the beginning of January, the British alternative represented only a small percentage of the pollution in France. By making assumptions from UK data, we predicted that it would become dominant in late February – early March. On this basis, the Scientific Council said that the situation is likely to deteriorate from March. So this first analysis turned out to be correct.

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At the time, the epidemic was rapidly returning to France, and a curfew was imposed on January 16. At the time, we did not have an accurate assessment of the potential effect of this procedure, and the only data we showed was that its effect on mobility was poor. With Vittoria Colizza, at Inserm, we made forecasts aimed at predicting the dynamics of the epidemic in a scenario where this curfew had no significant consequence. In this situation, one can expect to obtain a high level of hospitalization in the short term. Here’s what we posted on January 29th, and we’ve received a lot of comments since then.

“When we look at all of our work, I think these models provided useful information.”

But in reality, this rapid increase in cases hasn’t finally happened …

No, but very quickly after this first release, on February 2, we revisited these expectations by looking at the bigger impact of the curfew. On February 8th, we produced new analyzes to estimate its impact. This work showed that without strengthening measures, we risked reaching a hospitalization level for the second wave in early April, and a threshold of 50,000 cases per day. This is the situation we find ourselves in today. So, when we look at all of our work, I think these models provided useful, often verified, information. We’re in a scientific process, with hypotheses that have been verified and some don’t. It’s a job that never stops evolving, with its share of failures and successes.

Wasn’t Emmanuel Macron aware of all your work?

All of our analysis has been shared with the government. The president has tough decisions to make and he depends on the data he wants. On our part, we provide studies that we update as new data becomes available.

But how do you live the truth about warning about the deterioration of the situation, and seeing that the necessary measures are slow to take action, with all the consequences that result from hospitalization and death?

In the context of great uncertainty, we run the analyzes to try to better understand the health situation and pass it on. On their part, politicians have to make very complex decisions by considering health status and also other criteria such as impact on mental health, economics and acceptability of measures. Faced with the challenges of this crisis, it is up to politicians to make decisions.



Credit: LAURA ACQUAVIVAWritten by Christoph Donner


France, Paris, December 14, 2019, Portrait of Francois Bazin.Francois Bazin


Every week, Bookstore of the eco delivers a headline in the news.Written by Francois Roche


Frederic Velux.Frederic Philo


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