The findings marked the conclusion of a three-month study into the prevalence of the virus, which involved testing almost 70,000 people across Spain three times in as many months.
The results confirmed initial reports in May that a low percentage of people in Spain had developed antibodies after being infected with Covid-19.
In an article published in the health journal the Lancet on Monday, the scientists behind the study said: ”Despite the high impact of COVID-19 in Spain, prevalence estimates remain low and are clearly insufficient to provide herd immunity.”
”This cannot be achieved without accepting the collateral damage of many deaths in the susceptible population and overburdening of health systems. In this situation, social distance measures and efforts to identify and isolate new cases and their contacts are imperative for future epidemic control,” they added.
The study also discovered that 14 per cent of people who tested positive for antibodies in the first test produced a negative result in the final test, which implies that immunity to Covid-19 can be short-lived. This phenomenon was most common among those who never displayed symptoms.
As a result, Dr Raquel Yotti, director of the Carlos III Health Institute which co-led the study, said: ”Immunity can be incomplete, it can be transitory, it can last for just a short time and then disappear.”
After appealing to Spaniards to remain careful, she added: ”We can’t relax, we must keep protecting ourselves and protecting others.”
Spain, which has been one of the European countries worst affected by the pandemic, has recorded 28,385 deaths from coronavirus so far. It is still struggling with regions outbreaks, including one that led to the lockdown of more than 200,000 people in Lleida province in the northeast of the country last week.
The Spanish study report came a month after the results of an antibody study in Switzerland involving 2,766 participants were published in the Lancet. It suggested that a low percentage of the population in Geneva tested positive for antibodies, despite the city being a hotspot for the disease.
Additional reporting from Reuters