With the onset of winter, France – like many other countries in the northern hemisphere – is witnessing an increase in Covid-19 cases. Does this mean that the epidemic is starting again, as was the case a year ago to the day? Arnaud Fontanet’s answers.
For the Professor Arnaud Fontanet, epidemiologist at the Pasteur Institute, the reasons are multiple, he explains this Sunday in JDD columns. Starting with the change of weather report.
“The trend will be clearer in two or three weeks”
Indeed, the arrival of the cold mainly changes our habits. And it is in this sense that the winter climatic conditions favor the transmission of virus : “With the arrival of autumn, we go back to living indoors, windows closed. (…) With nearly 5,000 cases per day, France is in an intermediate situation: it is a recovery moderate epidemic. The R [nombre de personnes contaminées par un cas positif] just crossed the 1 bar. But beware, the trend will be clearer in two or three weeks because the change in our testing practices blurs the picture. You have to wait a bit to be able to identify a trend “.
“The drop in vaccine efficacy will be felt from November”
But according to Arnaud Fontanet, the increase in contamination and therefore the circulation of the virus should continue “because of two factors: weather and declining vaccine effectiveness against infection. Although the latter continue to provide more than 90% protection against severe forms of the disease, protection against infection increases from 80% two months after the second dose to 50% after six months. However, many 18-49 year olds were vaccinated at the beginning of the summer. It is in this age group, often involved in outbreaks of epidemics, that the decline in vaccine effectiveness will be felt from November “..
Example : “In the United Kingdom, where the vaccination began two months before France, and where almost all control measures for the epidemic have been removed, this week has reached 50,000 contaminations and 1,000 daily hospitalizations. This shows that we cannot let go of everything “.
Third dose for all, vaccination of under 12s: “It’s too early”
The solution : “Completing the primary vaccinations”. And the famous booster dose for those over 65 and the most fragile: “A booster dose increases the concentration of neutralizing antibodies to levels five to ten times higher than those obtained after a second dose, decreases the risk of infection by ten times and the risk of hospitalization by twenty times, for example report to people who received two doses, but no booster dose “.
For all adults, “it is too early” to decide on the third dose. And with regard to vaccination of children under 12, Professor Fontanet believes that“we must analyze the benefit-risk”. Knowing that the example of the United States is not necessarily a good example with regard to the high rate of obesity.
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