Results from the final stage of a nationwide antibody study showed some 5.2% of the Spanish population has been exposed to the coronavirus, health officials said on Monday, confirming findings from earlier stages and adding to evidence that so-called “herd immunity” to Covid-19 is not realistic.
Reuters reports that the study, which tested nearly 70,000 people across Spain three times over the past three months, found the virus’ prevalence had not altered significantly since preliminary results were published in May.
It also suggested that immunity to the virus can be short-lived, with 14% of participants who tested positive for antibodies in the first stage subsequently testing negative in the last stage.
“Immunity can be incomplete, it can be transitory, it can last for just a short time and then disappear,” said Dr Raquel Yotti, director of Spain’s Carlos III Health Institute, which co-led the study.
The loss of immunity was most common among people who never developed symptoms.
Speaking at a news conference, she appealed to Spaniards to remain prudent, particularly those who had recovered from the virus and considered themselves immune. She said”
We can’t relax, we must keep protecting ourselves and protecting others.
The report reads:
The relatively low seroprevalence observed in the context of an intense epidemic in Spain might serve as a reference to other countries.
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 key finding is that most of the population appears to have remained unexposed to Covid-19, even in hotspot areas and despite Spain being one of the worst-affected European countries (with more than 28,000 deaths and 250,000 plus cases), according to a Lancet commentary published alongside the findings.
The Spanish study’s lead author, Marina Pollán, who is director of the National Center for Epidemiology, told CNN:
Some experts have computed that around 60% of seroprevalence might mean herd immunity. But we are very far from achieving that number.
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, reads the Lancet commentary, which emphasises the need for maintaining preventative public health measures.