Given the delta variant and its high incidence, it may seem illusory to achieve combined immunity only with vaccines, but experts say these are even more important in controlling the Govit-19 infection.
For months, collective immunity, that is, the threshold of people who have been vaccinated against the disease, has been seen as the cradle of the way out of the crisis. But like Grail, is it just a pipe dream? It all depends on the definition we accept, respond to the experts.
“If the question is ‘Can infection be controlled and controlled only by vaccination?’ not that“Epidemiologist Mircia Sofonia told AFP.
In fact, “Two parameters are involved: the intrinsic infection of the virus and the effectiveness of the vaccine depending on the infection. This is not enough “, He continues.
Now dominant, the delta variant is 60% more prevalent than the previous one (alpha) and more than twice the historical virus. However, the more infectious the virus, the higher the threshold required for joint immunity (which is obtained through vaccines or natural infections).
“From a theoretical point of view, this is a very easy formula to calculate“, Epidemiologist Antoine Flauhlt explains to AFP.
The calculation is made from the base reproduction rate (or R0) of the virus, which is the number of individuals who are infected in the absence of control measures.
More than 100% of people should be vaccinated
Performance is low
Combined immunity threshold for historical virus (3 out of R0) “At 66%“Immunity,” recalled Professor Flaholt. “If R0 is 8 like the delta variant, we get 90%”, He continues.
This threshold can be reached if vaccines against infection are 100% effective. But this is not the case.
The effectiveness of the Pfizer and Modern vaccines has dropped from 91% to 66% since Delta dominated the United States, according to data released Tuesday by U.S. officials.
In addition to the characteristics of the variant, it may be related to the fact that performance decreases over time: it decreases from 88% to 74% after five to six months for Pfizer, and from 77% to 67% from four to five. Months for AstraZeneca, according to a British study released on Wednesday.
This is what drives most countries to consider a booster dose (often a third dose).
All of these parameters lead to a mathematical absurdity: to achieve joint immunity without any barrier gesture “More than 100% of people should be vaccinated”, Mr. Sophonia insists.
One goal by one of the fathers of the astrogenic vaccine is considered illusion.
“With the current variation, we are in a situation where joint immunity is not possible because it affects people who have been vaccinated.Professor Andrew Pollard (University of Oxford) made the announcement on 10 August in front of the British delegation.
When scientists were told to wear condoms during AIDS epidemics, many responded ‘For now, a little while’, eFinally we continued
But the vaccine has changed the herd’s immunity. “A mythIn the words of Professor Pollard, experts insist that vaccinations are necessary.
“Scientists recommend maximum public safety“, dit le Pr Flahault.
First, vaccines can be very effective in preventing severe forms of the disease and hospitalization.
Then, they provide collective protection for those who cannot benefit from the vaccine: this is for individuals whose immune system is weakened by another disease (cancer or transplant, for example).
Finally, it is possible “Achieve joint immunity, but not only through vaccinationAction “, assesses Mircia Sofonia.
This includes maintenance “The mask and forms of social distance, especially in certain areas“Control the virus, so as to minimize the risks as much as possible.
“When scientists were told to wear condoms during AIDS epidemics, many responded ‘For now, a little while’, eFinally we continued“, Says Antoine Flahold.We can wear the mask in closed places and transport for a while.
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