What is “collective immunity” to coronavirus?
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2020-03-24T16:10:24.353Z While some countries have adopted the strategy of collective immunity, before changing their mind, focus on this method rather criticized by scientists Two British in London, wearing masks.
For ten days, while France had taken containment measures, Boris Johnson was banking on collective immunity.
But the UK has changed its strategy.
- Matt Dunham / AP / SIPA The United Kingdom had for a time chosen to bet on "collective immunity" to avoid confinement and blockage of the country.
But for the past few days, these two countries seem to have changed their minds.
When you reach a reproduction rate of 1, the epidemic no longer spreads. "
This is why some countries have chosen not to confine populations, hoping that a rapid spread of the virus, once it has affected 60% of citizens, would provoke protective collective immunity in the long term.
Find our file To illustrate this concept, Mircea T. Sofonea, lecturer in epidemiology and evolution of infectious diseases at the University of Montpellier, takes an analogy: "An epidemic can be represented as a forest fire that spreads quickly.
The first models were published in the 1930s.
Working on Spanish flu at the start of the 20th century, mathematicians discovered that an epidemic does not die "for lack of combatants" - a situation in which the infectious agent would eventually disappear with the patients he kills - but by acquiring "gregarious immunity", explains Antoine Flahault, specialist in public health and epidemiology at AFP.
But this concept is mainly used to fight epidemics when you have a vaccine, to determine the rate of vaccine coverage necessary, to be sure that smallpox or measles will disappear, for example.
Little by little, some countries that wanted to build on this approach have revised their copies.
At first, the British Boris Johnson popularized the term "collective immunity".
While France imposed confinement on the entire population (with some exceptions), our British neighbors were invited to wash their hands.
If the Prime Minister, Mark Rutte, no longer excludes a total containment of the population, he hopes "that it will not be necessary".
Mark Rutte had declared last week wanting to favor the development of a collective immunity in the Netherlands of which, he had warned, most of the inhabitants would be contaminated.
The only European country to go it alone, Sweden has not followed the path of containment.
Another concern: there are still a lot of questions about this Covid-19.
And one of the questions is about long-term immunity to this coronavirus: basically, can you get this disease twice?
"For Sras, a coronavirus close to Covid-19, studies have shown that antibodies can drop after two years," says Mircea T. Sofonea.
This means that for this close virus, immunity is not guaranteed for life.
Please note that this cannot be transposed to Covid-19, which has only been discovered since December.
No one can tell you if people who have been infected will have a persistent immune memory within a year.
"Nothing says that group immunity is sufficient if the pandemic continues in other countries, that it circulates there quietly," continues the expert.
And come back in a few months with mutations such that our immunity would not recognize it.