At first glance, the figure would be surprising.
40% of positive Covid-19 cases in Israel would be vaccinated, according to the former director general of the Ministry of Health.
Another often-cited example comes from the UK, which provides very detailed data.
Among those over 50, 39% of those who were hospitalized had received two doses of the vaccine and were therefore as protected as possible, according to Public Health England.
In both cases, some immediately saw it as proof of the supposed ineffectiveness of vaccines.
However ...
Admissions in 50+
✅ 33% unvaxxed
✅ 27% partly vaxxed
✅ 39% fully vaxxed
First to note, as Delta is now dominant, this data is increasingly no longer just 'a Delta thing'.
Rather it reflects overall vaccine + COVID-19 surveillance in England.
- Meaghan Kall 🏳️🌈 (@kallmemeg) June 25, 2021
What you may have heard
"The proportion of those vaccinated among the positive is increasing, and we do not have the impression that it is radically different from that of the unvaccinated," the elected sovereignist Florian Philippot was carried away on Twitter on Tuesday.
He took up a sentence uttered in his last video by Didier Raoult, concerning the Marseille IHU which he heads but after having mentioned the situation in Israel.
Pr Raoult in his new video: "The proportion of vaccinated among the positive is increasing, and we do not have the impression that it is radically different from that of the unvaccinated"
And the same severity / mortality in vaccinated and unvaccinated.
Uplifting!
⤵️ https://t.co/265Iqt489M
- Florian Philippot (@f_philippot) June 29, 2021
"For the preservation of serious forms [in the United Kingdom] we will pass again", asserts on the social network another Internet user.
His message was notably shared by singer Francis Lalanne, also "antivax".
Why everything can be explained
In fact, these percentages - as high as they may seem - make sense when high immunization coverage is achieved. This is also the case in Israel and the United Kingdom, where respectively 60 and 50% of the population is fully vaccinated. These rates are much higher among adults only, and even higher among the elderly.
To fully understand, we must nevertheless hang on a little: let's take a virtual group of 10,000 inhabitants, faced with a virus that affects one in 100 people without protection (risk of infection of 1%).
If no one is vaccinated, we have 100 infected (including 0% vaccinated!) If 90% of this population is protected with a vaccine that is itself 90% effective, we end up on the one hand with 9,000 people vaccinated , of which no longer 1% but 0.1% will be infected, or 9 people - and on the other hand 1000 unvaccinated people, of which 1%, or 10 people, will be infected.
So here we are with 19 infected ... including 9 vaccinated, almost one in two.
The same demonstration can apply to hospitalized patients or to those who have died.
Of course, this mathematical logic must be adapted to the vaccination coverage in each country, the efficacy rate of the vaccines used, the local context (number of tests, restriction measures), etc.
But it explains why we can fall on significant proportions of vaccinated among the positive or hospitalized people.
Read also Delta variant: hospitalized but yet vaccinated, what the data on English patients say
As vaccination coverage with two doses in Israel is "only" 65% in the whole population (including children), "a share of 40% of vaccinated among infected patients seems a little high, but it has nothing to do with it. aberrant ”, indicates the mathematician Jean-Stéphane Dhersin, specialist in epidemics. "The higher the vaccination coverage, the more people will be infected while having been vaccinated," he adds. Taking logic to the end, if 100% of the population were vaccinated, the proportion of vaccinated among those infected or hospitalized would be… 100%.
“The right indicator to follow is the incidence rate in the vaccinated population and that in the unvaccinated population,” adds Jean-Stéphane Dhersin.
To come back to our example, there would therefore be 9 positive cases in the group of 9,000 vaccinated, ie 1 in 1,000, and 10 positive cases in that of the 1,000 unvaccinated.
In summary :
It is not surprising that the share of vaccinated among those infected, hospitalized or dead is increasing.
A vaccine is not 100% effective, and if an entire population is vaccinated, all positive, hospitalized, or deceased cases would be vaccinated.
