BEIJING (Reuters) – An antibody test against coronavirus that China has made mandatory for arriving travelers has raised concerns about its effectiveness after a team of international health experts briefly denied it last week. entry after a positive result.
Although the British expert from the World Health Organization (WHO) subsequently gave a negative result, it was not immediately clear whether the previous result was a false positive or the result of a previous infection or a vaccine against VOCID. -19.
Listed below are China’s testing rules, possible policy issues, their implications for vaccinated people, and expert opinions.
WHAT COVID-19 TESTS ARE NECESSARY?
Passengers from many countries, such as Canada, Germany, Singapore, and the United States, must show negative results from nucleic acid and immunoglobulin M (IgM) tests performed within 48 hours after boarding.
China uses IgM antibodies, which are usually detected in the first infections, as a complementary tool to filter those that may have been infected but get a negative result in nucleic acid testing.
However, some cases showed that IgM antibodies can persist for longer, and even after almost complete recovery.
WILL VACCINATED PEOPLE ACHIEVE POSITIVE ANTIBODY RESULTS?
It is possible, but not always, experts say. Most vaccines target the “spike” protein on the surface of the virus to elicit an immune response that could include IgM antibodies.
“We can assume that any COVID-19 vaccine containing spike protein will induce IgM, and therefore a diagnostic trial designed to detect spike-specific IgM will not be able to differentiate vaccination from infection,” said Helen Fletcher, professor of immunology at London School of Hygiene and Tropical Medicine.
Published data on the COVID-19 vaccine from Oxford University / AstraZeneca Plc show that in some people IgM caused by high protein can be detected at least 56 days after vaccination, Fletcher said.
Is it possible to use different antibody tests?
Tests to detect antibodies triggered by non-ear proteins may produce negative results for those who received ear protein vaccines, said Jin Dong-Yan, a professor of virology at the University of Hong Kong.
Spike protein-targeted vaccines include those from AstraZeneca, Pfizer Inc. and its partner BioNTech and Moderna.
THERE ARE STILL PROBLEMS
However, these tests can be problematic for other types of vaccines, including whole virus-based vaccines used by several Chinese developers, according to some experts.
“When a person is injected with an inactivated COVID-19 vaccine based on whole viruses … there is a good chance that the person may also have a positive result from non-state-of-the-art IgM protein antibody tests.” said Ian Jones, a virologist at Britain’s University of Reading.
The Chinese health authority does not clarify whether the test is designed to detect antibodies triggered by ear proteins or other proteins. The National Health Commission did not respond to any requests for comment.
CAN VACCINED PEOPLE ENTER CHINA?
China does not say clearly how it decides to exempt vaccinated people from their requirements for negative antibody testing.
In response to a question on the subject, one of its Singapore embassy officials said a vaccinated foreigner can present a vaccination certificate and wait for an answer. China’s Ministry of Foreign Affairs declined to comment.
IS USING A VACCINE PASSPORT AN OPTION?
At the November G20 summit, Chinese President Xi Jinping proposed a global mechanism for the mutual recognition of health certificates, including nucleic acid testing.
Experts expect China to consider using a vaccine passport to replace the antibody test.
“A vaccine passport will make travel to China much less complicated,” said Huang Yanzhong, a health expert at the U.S. Foreign Relations Council’s think tank.
“As Western countries gain herd immunity through mass vaccination, they will begin to open their borders … If China continues to have such a strict testing requirement, its aviation, hotel and tourism industries will lose.”
The WHO remains cautious: it refrained last week from advising that world travel be conditioned on this test, citing “critical unknowns” about the effectiveness of the tests and their limited availability.
Reports by Roxanne Liu i; Yew Lun Tian in Beijing; Edited by Miyoung Kim and Clarence Fernandez