When looking at an indicator of the Covid-19 pandemic, it is good to know how it is calculated….
to understand where some inconsistencies come from.
For example, the official government website displays vaccine coverage greater than 100% in Paris, as the essayist Idriss Aberkane relayed it on Saturday, citing a “rigged” count.
We will explain everything to you.
What you may have seen go by
"Paris is vaccinated two doses at 103.1% according to [the government site] but apart from that the accounts are not rigged", blurted on Twitter the one who describes himself as a "hyperdoctor", accompanying his text of 'a' laughing out loud 'emoji.
His message, "liked" by more than 8000 Internet users, very quickly went viral.
Paris is vaccinated two doses at 103.1% according to https://t.co/5m3OxwJLjx but apart from that the accounts are not rigged 😂 pic.twitter.com/lOif1GH2sB
- Idriss J. Aberkane (@idrissaberkane) October 16, 2021
This 103% is obviously inconsistent and impossible in practice.
Apart from Paris, all the French departments also display rates below 100%.
How can this rate be explained?
Two organizations calculate vaccine coverage: Public Health France and Health Insurance.
But they don't use the same method.
Public Health France takes into account the number of people vaccinated in each department, regardless of where they live, compared to the number of inhabitants in the department in question.
It is on this that the government site is based.
"Share of the adult population completely vaccinated in the department or region selected, compared to the number of adult residents of the selected place", is it also indicated when you click on: "Find out more about the indicator".
Government site screenshot
Social Security, for its part, counts the vaccinations according to the place of residence of each person.
By reporting to the population, we come across real vaccine coverage.
For Paris for example, 77% of the entire population and nearly 90% of adults appear fully vaccinated, according to the latest data as of October 10 (the update is weekly).
Nearly 90% rather than 103%?
Such differences can be explained in particular by the fact that residents have been vaccinated at their workplace or in a vaccination center that is easier to access but located in a neighboring department, as Le Parisien had already explained in May. latest.
In this case, we can imagine Ile-de-France “stung” in the capital.
"It is so easy (...) to explain a priori why, close to the limit of 100%, there may be a calculation error", denounced Sunday Xavier Azalbert, the director of the publication of the site "France Soir" , repeatedly noticed for sharing fake news or conspiracy theories about the pandemic.
It is indeed improper to speak of “share of the population vaccinated” using data from Public Health France, as the government does on its dashboard.
An internal source tells us that this choice would have been made in order to keep a single reference, in this case Public Health France, which also provides daily the number of tests carried out, positive cases, hospitalized patients, etc.
What exactly is the reality?
In reality, even the health insurance data remains imprecise.
Because if the numerator (the number of inhabitants vaccinated in a given department) is a priori correct, the denominator (the population) is not necessarily so.
Like Public Health France, Social Security uses data from INSEE, namely 2,154,092 inhabitants for Paris.
But the latest estimate for 2021 is 2,142,366, and the gaps are larger in some departments.
Above all, it is impossible to know how many people live in each territory at the moment T. The departures of Parisians who have left to settle in the provinces with teleworking, for example, are by definition not yet taken into account.
Read also Covid-19: why vaccine coverage is necessarily imprecise
Vaccine coverage by age group is also impacted.
“The population of the seventies is increasing, then all the generations of baby boomers will come out of this age group whose number of inhabitants will decrease.
Overall, in recent years, the population aged at least 65 has tended to increase, ”recently told us Sylvie Le Minez, head of the demographic and social studies unit at INSEE.
Thus, the number of inhabitants in the 70-79 age group today in France is probably greater than that appearing in the most recent censuses carried out in recent years.
More inhabitants in reality than for the calculation?
Logically, this can lead to an overestimation of immunization coverage.
In summary :
The government site displays a vaccination coverage of 103% among adults in Paris, which is explained in particular by the fact that all people vaccinated in Paris (and not just those who live there) are taken into account.
Health Insurance data are more precise, because they are based on the place of residence of each person vaccinated.
The vaccine coverage is a little imprecise anyway, since the population of a territory is impossible to know at the moment T.
