Cocorico, France is among the most vaccinated countries in the world (in terms of percentage), has overtaken former champions Israel and the United Kingdom, and presents figures which seemed unattainable a few months ago: 77.8% of the population eligible for the vaccine, i.e. French people aged 12 and over, is fully vaccinated against the coronavirus, a rate that is around 85% among those over 60, i.e. the population most at risk.
But triumphalism does not have time to take hold. According to the Institut Pasteur models posted online this Monday, even with even higher vaccination levels (70% of 12-17 year-olds, 80% of 18-59 year-olds and 90% of 60-year-olds and over), he epidemic could start again. If all barrier measures are lifted, France could experience a peak of 5,200 daily hospitalizations, well above the first or second wave.
Vaccinated and contaminated, so what?
This disaster scenario is mainly carried by the unvaccinated, unvaccinated over 60s (barely 10% in the hypothesis) thus represent 3% of the population for 43% of hospitalizations. But this peak also owes a lot to the Delta variant. According to some studies, this variant is 60% more transmissible than the Alpha variant, itself 50 to 74% more transmissible than the original strain of Covid-19. As a result, it contaminates more, also in the vaccinated.
For many weeks, cases of vaccinated positive for the coronavirus have been rising. Cases that are in reality nothing surprising or unexpected, for several reasons. First, the initial goal of the vaccine was never to fight against coronavirus contamination, but against the risks of hospitalizations and serious forms, recalls the doctor of Public Health Mickaël Ehrminger. Then, because the more the population is massively vaccinated, the more the number of contaminated vaccines increases, logically. Simple logic explained by a reasoning by the absurdity of the doctor: “If 100% of the population is vaccinated, 100% of the infected will be vaccinated. “.
However, the Delta variant effectively decreases the protection of the vaccine against contamination. The percentage is extremely difficult to calculate, so different numbers come out on almost every study. According to a real-life study in Israel, the vaccine no longer protects “only” 64% against contamination in the Delta. According to the Director General of Health in France Jérôme Salomon, vaccinated people are eight times less likely to be infected than unvaccinated people. But this conclusion was established according to the figures of positive tests, but vaccinated people are less tested, a fortiori in France (where a test is necessary for the unvaccinated for many daily activities). This interpretation therefore suffers from numerous biases, proof of the complexity of establishing these figures.
Efficacy confirmed on severe forms
One thing is certain, the Delta variant has increased contamination and transmission, especially among vaccinees. Immuno-oncology researcher Eric Billy nevertheless recalls: “Even in the face of this variant, the vaccine has a notable impact on contamination and transmission. We must not forget that even if the vaccine for example only reduces the risk of being contaminated by two, we de facto decrease in a vaccinated population the reproduction rate of the virus by two, it is enormous. “
Above all, and this is the most important, the vaccine retains almost all of its effectiveness against severe forms, Delta or not, that is to say more than 90%, recalls Doctor Mickaël Ehrminger. And this, even if you are infected with the coronavirus. It is therefore necessary to read the studies on the effectiveness of vaccines to see what they are about: effectiveness against contamination, against transmission, or against severe forms and deaths. So we repeat it a second time, it does not hurt: the effectiveness of vaccines against severe forms and deaths remains at levels above 90%, regardless of the variant of the virus.
The end of the dream of collective immunity
Everything is fine then, this increase in contaminations and transmission with Delta even among vaccinated people is therefore of no importance? Well not at all. With a vaccinated population more contaminated and more transmitting because of Delta – even if here too, it should be noted that the vaccine also decreases the transmission of the virus to other people, even with Delta – this is the dream of the collective immunity that goes up in smoke. Reminder with Eric Billy: “Collective immunity is the necessary proportion of vaccinated or immunized people in a population so that the virus no longer circulates and therefore does not contaminate the unvaccinated”. However, the researcher continues, “the Delta changes the situation, it will take many more people vaccinated than expected so that the unvaccinated are not reached. “
This is what explains the disaster scenario of the Pasteur Institute: the virus will circulate and eventually reach the unvaccinated. As the study shows, it only takes very few unvaccinated contaminated people to give astronomical figures for hospitalizations and deaths. But in fact, if collective immunity is almost unattainable, is there still an interest in vaccinating populations not at risk, especially young people? Yes, even beyond the fact that there is no zero risk of catching a severe form of the virus. “Vaccination remains interesting for non-fragile groups because it still contributes to reducing transmission, even if it does not reduce it to zero,” explains Mickaël Ehrminger.
Concretely, “even if we cannot achieve collective immunity with vaccination, getting vaccinated will necessarily break the chains of transmission of the virus and reduce, if not prevent, the circulation of the virus and will allow some non-vaccinated people to do not catch the virus, therefore reduce the pressure on hospitals, ”says Eric Billy. Added to this is the fact that the less a virus circulates, the less chance it has to mutate and create an even more dangerous variant. What convince oneself to be vaccinated, while maintaining certain other protective measures: ventilation, distancing, etc. so that the Institut Pasteur models remain theory.