Stockholm residents protected by May?

The Swedish capital is on track to achieve collective immunity against the Covid-19 coronavirus, the one that naturally stops the spread of the epidemic. Sweden is one of the few countries in the world to have opted for this strategy, considered too risky by many epidemiologists. Confining or letting the virus circulate: who was right in the end?

" We will reach collective immunity in Stockholm by next month "Guaranteed Swedish Ambassador to the United States Karin Ulrika Olofsdotter on April 26 at the radio american NPR. According to the diplomat, 30% of the inhabitants of the capital have already been infected by the coronavirus of Covid-19 and this rate should continue to increase to obtain a immunity collective capable of naturally stopping the spread of virus.

Unlike most European countries and the world, Sweden has chosen not to confine its inhabitants, schools, restaurants and shopping centers remaining open. However, the government has advocated respect for social distancing and bans gatherings of more than 50 people.

With nearly 20,000 cases and 2,355 deaths, Sweden is one of the worst students among the Nordic countries. Finland and Norway register 199 and 206 deaths respectively for a population only twice as low. But the country remains far ahead of Italy or France, which have more than 20,000 deaths due to Covid-19 and where very strict measures to confinement have been in effect for almost two months.

" We have reached a plateau (new cases) around Stockholm, where we are already seeing the effect of collective immunity, and the situation is stable in the rest of the country "Anders Tegnell, chief epidemiologist of the Swedish public health agency, assured the chain CNBC. In fact, the vast majority of cases are recorded in Stockholm and around Gothenburg, the country's two major cities, the rest being almost virgin.

Barely 6% of people infected in France

This optimism contrasts with numerous epidemiological studies. According to a study by the Institut Pasteur, barely 6% of French people should have been infected with the SARS-CoV-2 by May 11. AT New York, epicenter of the'epidemic of Covid-19 in the United States, the rate would reach 14%. same in confined places like the cruise liner Diamond princess, only 19% of passengers and crew were affected. Far from the 60% required for effective collective immunity.

This rate is itself the subject of lively debate within the scientific community, some estimating it at 50 or 80%. For the mumps for example, it is estimated that the rate of vaccination must be 92% for the virus to stop circulating. It actually depends on the virus contagiousness, calculated by the number of people infected by a single patient (reproduction rate, noted R0).

Above all, many doubts have emerged in recent weeks about the famous acquired immunity by individuals once infected with the coronavirus. Several possible cases of re-infection have been recorded in patients, and it is unclear whether duration protection antibody, or even their effectiveness. " Some people develop a very good immune response by producing lots of antibodies that can effectively neutralize SARS-CoV-2, and others don't. ", Indicates Hugo Mouquet, head of the humoral immunology laboratory (Inserm / Institut Pasteur).

Confinement vs collective immunity, what strategy to stop the epidemic?

So, should we patiently wait to pass the 60% mark or confine to stop the spread of the virus, even if it means relaunching a second wave after the deconfinement? The example of Sweden will tell us, knowing that the strategy of collective immunity can only work in countries with a hospital system capable of supporting a large number of patients who will develop severe forms of Covid-19. Sweden, on the other hand, can boast of having limited an economic disaster to the repercussions that are still unknown, as Italy or France will experience.

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