Dr Karine Lacombe, infectologist and head of infectious diseases at Saint-Antoine hospital in Paris, told a news source BFMTV that, with a vaccine that is 95% effective: “If 50 to 60% were vaccinated, it would suffice to vaccinate the entire population.”
Vaccination is considered an effective strategy against the Covid-19 virus, because immunizing people against the disease through vaccination reduces the number of hosts that can catch and spread the virus. But polls have shown that people France is less likely to get vaccinated than anywhere else in the world.
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The success of the vaccine depends on the number R
Professor Jean-Stéphane Dhersin, epidemiologist and deputy director of mathematical sciences at the CNRS research center, said BFMTV that the percentage needed to obtain the vaccine is closely related to the number R.
He said: “In terms of collective immunity, it’s hard to know where we are because it depends on which R number is less than 0. We have to make sure that the R number does not go over 1. [Then] to guarantee collective immunity, we need to be around 60% of the vaccinated population.
Official figures show that the current R number in France is 1.03. This means that each person infected with Covid-19 will continue to infect 1.03 other people.
Figures from the national ministerial center of statistics DREES show that 11% of the population (6.33 million people over the age of 15) in France have had Covid-19. While having had the virus does not guarantee immunity, cases of reinfection are rare, so this 11% can be considered immune to the virus.
Professor Dhersin said: “We are now over 10% [immunity], but if we have effective vaccines that could increase up to 55%, then we would be between 50 and 60% and herd immunity would be achieved.
But other doctors take a more cautious view. Professor of virology at the Sorbonne, Vincent Maréchal, tells BFMTV that current projections were all based on “assumptions”.
He said: “We still don’t know if the vaccine blocks transmission of the virus. We know it stops disease and severe cases. [But] the polio vaccine does not stop the transmission of the virus. ”
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