Achieving herd immunity to coronavirus through natural infection is “unethical,” “unachievable,” and risks a second wave of COVID-19, according to two scientists who analyzed recent studies of immunity levels in infection hotspots.

Writing in the scientific journal the Lancet, Isabella Eckerle and Benjamin Meyer analyzed recent studies regarding the level of immunity reached in countries that witnessed significant outbreaks including Spain, Switzerland and China.

According to their assessment, the studies undermine the idea that a form of natural resistance to COVID-19 could be developed through the majority of the population catching the disease and then developing immunity to it – the strategy known as “herd immunity.”

“The key finding from these representative cohorts is that most of the population appears to have remained unexposed to SARS-CoV-2, even in areas with widespread virus circulation,” wrote the authors.

 

Low level of spread even without lockdown

The two authors added that only low levels of “seroprevalence,” or exposure to the disease, had been found even in countries that did not impose lockdown measures, such a Sweden, which attracted attention for its strategy to try to achieve some form of herd immunity.

The authors further argue that detecting seroprevalence does not mean that people who have been infected with the disease are immune to being infected again, and that scientists still do not know whether humans will develop lasting and strong immunity to COVID-19.

Considering all these factors, the scientists concluded that any attempt to allow COVID-19 to spread through the population is dangerous and could lead to a second wave of the virus, such as waves seen in Serbia and the Australian city of Melbourne, where lockdown measures were lifted and then re-implemented after a rise in cases.

“Any proposed approach to achieve herd immunity through natural infection is not only highly unethical, but also unachievable. With a large majority of the population being infection naive, virus circulation can quickly return to early pandemic dimensions in a second wave once measures are lifted,” they wrote.

However, they added that seroprevalence studies were of some use for authorities to calculate exposure rates to the disease, especially in areas where they lacked testing.