As the world grapples with when and whether to lift social distancing restrictions imposed due to the pandemic of coronavirus, officially called COVID-19, one suggestion that has been floated is the use of “immunity passports.” The idea is that people could be tested to see if they have the antibodies to coronavirus, which is one indication that they may have developed immunity to the virus. Those who have antibodies could be issued passport-like documents that would allow them to travel or work in areas where the virus is still widespread.
But the World Health Organization (WHO) wants to put the kibosh on that plan. This week, it released a scientific briefing warning that even people who have antibodies may be vulnerable to being reinfected. So just because you have had coronavirus once, that doesn’t necessarily mean you won’t get it again. This makes the idea of immunity passports unfeasible.
“At this point in the pandemic, there is not enough evidence about the effectiveness of antibody-mediated immunity to guarantee the accuracy of an ‘immunity passport’ or ‘risk-free certificate.’,” the WHO briefing read. “People who assume that they are immune to a second infection because they have received a positive test result may ignore public health advice.”
Antibodies are produced by the body as part of its immune response to a virus. These antibodies bind to the virus and neutralize it. Several studies have shown that people who recover from coronavirus do have specific antibodies for the virus. However, there is also a second response which is relevant, called cellular immunity, in which the body’s T-cells recognize and eliminate cells that are already infected with the virus.
The problem with antibody tests is that some people who have recovered from coronavirus have only low levels of antibodies, so it looks as if cellular immunity is also important in recovering. It’s possible that people with antibodies could become re-infected if they don’t have sufficient cellular immunity.
Another issue is that tests for COVID-19 are very new, and like any diagnostic test, can show false positives or false negatives. Also, as COVID-19 is only one of a family of six coronaviruses known to affect humans, an antibody test may not be able to distinguish between antibodies for COVID-19 and antibodies for one of the milder viruses which are common and cause cold-like symptoms.
Research into antibody tests will continue and it’s possible that new findings will make the tests more accurate and reliable. But for now, it looks like immunity passports won’t be a good solution to the current crisis.
For the latest updates on the novel coronavirus outbreak, visit the World Health Organization’s COVID-19 page.
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