A World Health Organization official said Wednesday that the international agency does not recommend countries issue so-called immunity passports for the coronavirus, because scientists are still unsure whether Covid-19 antibodies reduce the risk of reinfection.
Earlier in the pandemic, some countries said they would issue passports or certificates that indicate whether someone has had Covid-19, allowing them to travel or return to work, assuming that they are protected.
That idea has since been abandoned because scientists still don't know how long immunity really lasts, Dr. Jarbas Barbosa, assistant director of the WHO's Pan American Health Organization, said at a press briefing on Wednesday.
"We do not have that information. Therefore, that person may receive that passport and believe that they're duly protected and later on have a new infection because the immunity may only last a couple of months," Barbosa said. "We do not know. For that reason, we do not recommend that."
Antibodies are generally produced in response to foreign particles or antigens that invade the body and help the body's immune system fight off infections. Health officials have said there is not enough data yet to indicate that coronavirus antibodies ensure immunity against the virus.
A small study published in Nature Medicine in June showed that coronavirus antibodies could last only two to three months after a person becomes infected with the virus. Researchers in the Wanzhou District of China compared the antibody response of 37 asymptomatic people with that of 37 symptomatic people. They found that people without symptoms had a weaker antibody response than those with symptoms.
But scientists say it's unclear if no antibodies or low levels of antibodies mean that a person is actually at risk of reinfection if reexposed to the virus.
In June, Dr. Anthony Fauci, the nation's leading infectious disease expert, said if Covid-19 acts like other coronaviruses, "it likely isn't going to be a long duration of immunity."
"When you look at the history of coronaviruses, the common coronaviruses that cause the common cold, the reports in the literature are that the durability of immunity that's protective ranges from three to six months to almost always less than a year," he told JAMA Editor Howard Bauchner. "That's not a lot of durability and protection."
Duration of immunity has important implications for vaccine development. Even if a person loses immunity after a period of time, if scientists discover how long immunity lasts, they may be able to recommend when a person may need another vaccine dose.