New study says herd immunity is a myth and countries relying on it, including Sweden, chose the wrong strategy

Herd immunity may be an unrealistic tactic for dealing with Covid-19, new research has warned, calling into question the strategy of several countries – such as Sweden – who shied away from quarantine measures in its favor.

Europe is a long way from reaching the levels of exposure required for herd immunity, according to a new study published by the Italian Institute for International Political Studies (ISPI). Belgium tops the list, with just 6.2 percent of its population exposed to Covid-19 so far, and Sweden – with no enforced lockdown measures – is even lower down the list at just 2.5 percent. The latter figure is a far cry from the 40 percent May total promised by a top Swedish epidemiologist.

“Even if these numbers were underestimated by 50 percent, the majority of people will continue to be exposed to the virus; mass immunity is a fantasy,” said Carlo Rosa, chief executive of DiaSorin, an Italian biotech company producing Covid-19 testing kits for Europe, in an interview to the Financial Times. “Nobody knows what will happen next; we must be prepared, especially when the annual flu season begins in the autumn.”

In order to reach any level of herd immunity, the proportion of those exposed to the virus would have to be over 70 percent, according to the study – 28 times the number currently recorded in Sweden. Since the outbreak of the deadly pandemic, Sweden has been a global outlier by choosing not to lock the country down to prevent further infections.

Sweden's approach has also come under heavy criticism for having a considerably higher death toll than its Nordic neighbors – it has recorded 3,313 coronavirus-related deaths so far, compared to just 224 in Norway and 271 in Finland. This has raised questions about how many people would need to die in order for herd immunity to develop; 22 doctors came forward at the end of April to publicly condemn Sweden's approach and the “officials without talent” who spearheaded it. 

The WHO also spoke out negatively about the idea of herd immunity on Monday, calling it “brutal arithmetic.” 

Nevertheless, the possibility of herd immunity has permeated mainstream media outlets, some of which have pointed out that finding an effective Covid-19 vaccine will take many months, which would mean herd immunity is the only alternative approach that would allow economies and countries to reopen in the near future. If the numbers published by the ISPI are true, then Sweden's gamble has not paid off. Instead, as the ISPI study suggests, countries should rely on “extensive testing, tracing, and treatment of the disease.”

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