A large-scale Spanish medical study published on Monday found that achieving nationwide "herd immunity" to the new coronavirus is far from the current reality and that social distancing measures remain the best approach to dealing with the pandemic.
Only 5% of the over 61,000 participants developed antibodies that would be able to fight the disease, according to the research partly funded by Spain's Ministry of Health and published in the Lancet Journal.
The study also found that around one-third of participants who had contracted the virus remained asymptomatic, which the authors say has "important public health implications."
"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," researchers said.
Herd immunity is achieved when enough of a population has become infected with a virus or bacteria, or vaccinated against it, to stop its circulation.
"Some experts have computed that around 60% of seroprevalence might mean herd immunity. But we are very far from achieving that number," lad author Marina Pollan told CNN.
According to the study the results emphasize the need for maintaining social distance measures and continue efforts to identify and isolate new cases and their contacts "for future epidemic control."
The authors said it is unclear whether someone who has been infected with the virus but who has not developed antibodies could be reinfected.
The research, conducted by leading government research and epidemiological agencies, began in April, while Spain remained under a strict lockdown.
Spain has been one of the European countries hardest hit by the pandemic, with more than 28,000 deaths and 250,000 cases.