ROME — Cooped up, stir crazy and desperate for their lives back, many Europeans and Americans have seized on antibodies and their promise of potential immunity to the coronavirus as the golden ticket to reopen societies and economies.
Not long ago, politicians in Italy — which, as the epicenter of Europe’s contagion, is further in the pandemic’s cycle than other Western nations — proposed issuing licenses to those who had beaten the virus and developed the right antibodies to get back to work.
Researchers and politicians in China, the United States, Germany, Britain and beyond have latched onto antibodies as a potential solution to the virus and an outlet from containment measures.
But that talk, always ahead of the science, has grown more muted in recent weeks. With the research refusing to cooperate, experts in Italy say the promise of antibodies may not be what people have imagined. At least for now.
“We don’t know if everyone who has had the disease has developed an acceptable protective immunity,” said Dr. Alessandro Venturi, the president of the San Matteo hospital in the Lombardy town of Pavia. The hospital validated the antibody screening test used for mapping the virus in Lombardy, Italy’s hardest hit region.
Infected people develop different quantities of antibodies, and researchers are still studying the level that offers protection, and for how long.
“We don’t know how long they last,” Dr. Venturi said. ‘‘This is the central point.”
That is tough news not only for Italy, which is loosening its lockdown on Monday, but for the rest of the world.
Italy’s government will soon start testing 150,000 people for antibodies for a “sample survey on the spread of the infection,” according to its website.
Many regions, including Lombardy and Veneto, are still doing such screenings. But whereas last month the presidents of those regions promoted the idea of issuing licenses to members of an immune work force, now they have downgraded the tests from panacea to a research tool.
“Immunity licenses are just rubbish,” said Mario Plebani, the coordinator of the antibody tests for the Veneto region.
Politicians and experts have tried to lower expectations. But that has not stopped citizens, desperate to know if they have had the virus and are protected from it, and companies, eager to return to normalcy, from flocking to antibody screenings.
Many businesses in the region have been paying for employees to get the tests, so that they could go back to work if they tested negative for the virus or positive for the antibodies.
Dr. Venturi said those tests were essentially “useless” because they did not describe whether a person had the right level of antibodies and because no one knew yet how long they lasted.
Some virologists said they worried that all the hype around antibodies would lead to bad behavior among those who consider themselves invincible, thus leading to more infections.
“I am very worried that the irresponsible use of serological tests will jeopardize phase two,” the start of Italy’s reopening, Dr. Alberto Mantovani, a leading Italian immunologist, told the TV channel Sky TG24 last week.
But Dr. Venturi said antibodies with the ability to neutralize the virus still had important functions, including for developing plasma that could aid patients, and still held the potential for breakthroughs that could eventually help Italy reopen more fully.
His Humanitas research hospital near Milan treated Italy’s first known coronavirus patient and has deep experience with the virus. It has been examining the 2 or 3 percent of people in the region who swab tests show are actively infected but whose blood also contains the antibodies — known as immunoglobulin G, or IgG, antibodies — that should neutralize the virus. In other words, these people are no longer contagious.
In those cases, Dr. Venturi said, the virus did not replicate and cause a broader infection.
“It means it’s not contagious,” he said, adding that the hospital’s study is being scaled up as its researchers seek 200 such cases from throughout Lombardy, where they estimate 10 percent of the roughly 10 million residents have contracted the virus.
Locating those cases has not been easy considering the rarity of finding someone who has both the desired antibodies and the virus contemporaneously.
Results will take weeks more, but if confirmed, he said, it would show that people who test positive for an adequate level of neutralizing IgG antibodies do not pose a danger of contagion.
In theory, even those lucky few would not need to wait for two consecutive negative swab tests — which sometimes take months — before being released from quarantine and allowed back to work. “It would be like a negative test result,” he said.
In the meantime, though, Dr. Venturi said it was impossible to consider a work force made up only of people showing neutralizing antibodies.
Instead, he said, Italy’s reopening phase needs to rely on uninfected people, which he considered to be 90 percent of the population, and on social distancing and other protective measures.
In talking about immunity licenses, he said, politicians have “gotten ahead of themselves.”
This past week, the office of Lombardy’s president, Attilio Fontana, who had predicted that immunity licenses would be in place by April 21, said everyone still needed to follow recommended lockdown measures.
“There is no immunity license,” Giulio Gallera, the region’s top health official, said.
Still, as some mayors continue to promote antibody tests as a possible way out of lockdown, people have waited for hours in gymnasiums to have their blood drawn.
Paolo Passaggio, 45, an exporter of home appliances, jumped at the chance when the mayor of his small Lombardy town, Robbio, recently offered antibody screening.
“I did it to free myself of this doubt,” said Mr. Passaggio, who last month showed Covid-19 symptoms, including a low fever. Unable to get tested for the virus, as swabs are generally reserved for the hospitalized, he took precautions to avoid contaminating others, including staying isolated for weeks.
Last Tuesday he got the results: high levels of immunoglobulin G, or IgG, antibodies. Mr. Passaggio said he understood from doctors on television that it meant a degree of immunity, confidence he was not a danger to others and that he could possibly “go to work before someone else.”
Health experts say that is far from clear. But in any case, Mr. Passaggio said he did not plan to alter his behavior drastically. While he aimed to see his elderly parents for the first time in months, he expected to stay in the yard and wear a mask.
Some of Italy’s mayors, furious that testing for the virus has not been more widespread, argue that antibody screening is important psychologically, scientifically and practically. They have clung to the hope that immunity licenses will become available to those with the right antibodies.
“We were the trailblazers,” said Roberto Francese, the mayor of Robbio, which began testing in April. “Now, everybody is doing it.”
Mr. Francese said that a month ago, 50 people in the town showed clear symptoms of the virus, but that the health authorities failed to test them. They got sick, and then their relatives got sick and cases kept building.
The town, out of desperation, tracked down serological tests offered by a Chinese factory that the mayor said had an 96 percent accuracy rate, and which he said Italy’s national research center had approved.
Robbio has already tested about half of its residents and found and isolated many positive cases, about half of whom had symptoms, he said. He also said that the tests had shown 12 percent had IgG antibodies.
He said he considered those people “immune and thus would be eligible” for an eventual immunity license, despite health experts’ doubts.
Mayor Luca Dure’ of Cisliano, also in Lombardy, said tests showing the presence of protective antibodies would “determine a sort of license of immunity” at some point in the phase of reopening beginning on Monday.
“We don’t know how long, but surely for some months, they can remain in the blood for a year or two,” he said, calling this “surely a positive thing.”
Even someone with IgG antibodies must act responsibly, Mr. Dure’ said.
“It’s not like a person can go to the theater or dancing at the disco,” he said, but people could feel a measure of safety.
“We cannot wait anymore,” he said.
Emma Bubola contributed reporting from Milan.