The Pasteur Institute had already indicated that it would take a very important vaccination coverage to return to normal life next fall.
The emergence and spread of the Delta variant, which is highly transmissible and which could become the majority in France and throughout Europe by the end of August, further complicates the situation.
In a new model posted online this Monday, the same team of scientists is anticipating a fourth wave at the hospital next fall.
The basic scenario is as follows: an “R0” (the number of people an infected individual will infect on average without any control measure) of 4, vaccination coverage (with two doses) of 30% of 12-17 years, 70% of 18-59 years and 90% of over 60 years, and an effectiveness of vaccines against hospitalizations of 95%.
The number of daily hospital admissions in France could then climb to 2,500. This would be a little less than the peak of last autumn (2,850), but more than that reached at the end of April (2,000 ).
Weaker measures thanks to vaccination
Compared to last year, vaccination is obviously a game-changer.
In each segment of the population, unvaccinated people would be "over-represented among those infected", say the scientists.
All ages combined, the inhabitants who have not received any dose represent 37% of the population but 75% of infections.
The unvaccinated over 60s, or 3% of the population, even make up 35% of hospitalizations.
At the same time, thanks to the vaccine, the proportion of 18-59 among hospitalized patients would drop from 25% without the vaccination to 40%.
Read also Delta variant: hospitalized but yet vaccinated, what the data on English patients say
Above all, measures will limit the extent of this wave.
It is even "probable" that they are necessary.
But good news: There shouldn't be a need to go as far as real containment.
"It is a message of hope: thanks to the vaccination, the necessary effort will not be as great as what we have known," said the Parisian Simon Cauchemez, lead author of the study.
We studied how the epidemiology of SARS-CoV-2 could evolve in a partially vaccinated population.
Who will be infected?
Who will transmit?
Who will be hospitalized?
And what implications for controlling a possible rebound?
https://t.co/kExKl8oD7d pic.twitter.com/NhA2T81q7E
- Simon Cauchemez (@SCauchemez) June 29, 2021
Testing half of the population aged 12 and over and unvaccinated each week could reduce the peak of daily hospitalizations by 27% (with self-tests) or 32% (with tests done by professionals).
The most effective method, which can lead to an 89% lower peak, will remain to convince this group to be vaccinated.
Indeed, "unvaccinated individuals will contribute much more to the spread of the disease than the vaccinated", write the scientists.
If vaccination coverage climbs to 90% among 18-59 year olds, the peak of daily hospitalizations would rather be around 1,000.
Target the unvaccinated?
More “classic” measures, such as physical distancing or wearing a mask, would also have a significant impact. With a 10% reduction in the transmission rate, the peak hospitalizations would already be 37% lower. To reach these 10%, there is no need for confinement which "reduces the transmission rate from 70 to 80%", recalls Simon Cauchemez, who believes that we can achieve it "by respecting barrier gestures, by continuing to make a pay little attention to wearing the mask in certain situations, etc. ”.
Interestingly, the results would be almost the same if these restrictions only applied to unvaccinated people, for example by expanding the uses of the health pass.
Pasteur's team deduces that targeting these would make it possible to "maximize" the gain in terms of health while having a much less impact on the economic life of the country.
Read also Health pass: why 2 million French people tested positive for Covid-19 are deprived of sesame
But such a strategy would automatically lead to "discrimination" and would pose a certain number of "ethical questions", in particular for adolescents who are not in a position to decide for themselves to be vaccinated since the agreement of both must be obtained. parents. However, low vaccination coverage among minors will risk causing contamination and therefore class closures, "with a deleterious impact on the education and mental health" of the youngest. Imposing constraints on them (and on them alone) such as wearing a mask could also seem unfair. “We risk ending up in a scenario where widely vaccinated adults can resume more or less normal lives; but students continue to live with strict health protocols at school because they are not vaccinated.All this arouses my concern, ”anticipates Simon Cauchemez.
Without commenting further on all these aspects, he and his team insist that "the vaccination of the unvaccinated remains by far the most acceptable and cost-effective strategy" to control the epidemic. While recalling that many uncertainties persist, including the real “R0”. If it is instead around 5, hospitals will be much more likely to be overloaded with Covid-19 patients.
