Covid-19 herd immunity unlikely anytime soon as study shows just 5% of Spanish population has antibodies

A nationwide study in Spain has found that, despite being one of the hardest-hit European nations, just 5 percent of the population has coronavirus antibodies, dispelling any hopes of herd immunity in the near future.

The research, published in the widely respected medical journal The Lancet, began in April and included some 61,000 participants from a country with over 250,000 cases confirmed and over 28,000 deaths. 

Herd immunity is said to occur when the majority of a population has been vaccinated or developed antibodies to fight off a particular bacterial or viral infection. 

The concept of herd immunity was the main argument against the widespread lockdowns which were adopted in many countries. Sweden’s entire coronavirus response plan relied heavily on herd immunity rather than enforced restrictive measures. 

According to the authors of the study, roughly 95 percent of the general population in Spain remains susceptible to infection, though there are significant geographic disparities that coincide with the original rates of infection.

“At present, herd immunity is difficult to achieve without accepting the collateral damage of many deaths in the susceptible population and overburdening of health systems,” the report reads.

The first phase of the study was conducted between April 27 and May 11 and the second phase results were released on June 4, showing a 5.2 percent national prevalence of SARS-CoV-2 antibodies. The third-phase results will be released next Monday and are expected to align closely with the current figures. 

Madrid, Spain’s hardest-hit area, had an antibody prevalence of 10 percent while Barcelona had 7 percent antibody prevalence. A similar study conducted in Switzerland found the population in Geneva had a roughly 10.8 percent coronavirus antibody prevalence.

Studies conducted in the US and China yielded similar results, with the key takeaway in each case being that “most of the population appears to have remained unexposed.”

According to the Lancet's commentary authors, Isabella Eckerle, head of the Geneva Centre for Emerging Viral Diseases, and Benjamin Meyer, a virologist at the University of Geneva, proposals to actively seek herd immunity "not only highly unethical, but also unachievable.”

An additional flaw in the reliance on potential herd immunity is that experts remain uncertain about the potential for re-infection, or indeed how well or for how long antibodies might protect a person. The researchers also observed a loss of antibodies in participants who had displayed them in previous phases of the study. 

“The majority of the Spanish population is seronegative to SARS-CoV-2 infection, even in hotspot areas,” the study says. 

Other key points from the study were that researchers noted a less than 3 percent prevalence in certain coastal areas and a lower overall prevalence in children below 10 years of age.

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