BEIJING (Reuters) – A coronavirus antibody test that made China mandatory for incoming travelers has raised concerns about its effectiveness after one of a team of international health experts was briefly denied access to a positive result last week.
Although the British World Health Organization (WHO) expert subsequently tested negative, it was not immediately clear whether the earlier result was a false positive result or the result of a previous infection or a vaccine against COVID-19.
Here are details of China’s test rules, possible problems with the policy, its implications for vaccinated individuals and the views of experts.
WHAT TESTS OF COVID-19 ARE NEEDED?
Travelers from many countries, such as Canada, Germany, Singapore and the United States, should show negative results of the Nucleic Acid and Immunoglobulin M (IgM) test within 48 hours of boarding.
China uses IgM antibodies, which are usually detected early in infections, as a complementary tool to filter out those who may be infected but who get a negative result on nucleic acid tests.
However, some cases have shown that IgM antibodies can last longer, and even after almost complete recovery.
WILL AIMED POSITIVE ANTIBODY RESULTS GET?
It is possible, but not always, experts say. Most vaccines target the virus surface to the “spike” protein to elicit an immune response that may include IgM antibodies.
“We can assume that any COVID-19 vaccine containing the protein will cause IgM, and therefore a diagnostic test designed to determine specific IgM will not be able to distinguish vaccination from infection,” said Helen Fletcher, a professor of immunology at the London, said School of Hygiene & Tropical Medicine.
Published data on the Oxford University / AstraZeneca Plc COVID-19 vaccine show that muscle protein-activated IgM is detectable in some people at least 56 days after vaccination, Fletcher said.
IS IT POSSIBLE TO USE DIFFERENT ANTIQUE TESTS?
Tests to detect antibodies caused by non-ear proteins can have negative results for those who get vaccines that target ear proteins, said Jin Dong-Yan, a professor of virology at the University of Hong Kong.
Vaccines that target vein proteins include AstraZeneca, Pfizer Inc. and its partner BioNTech and Moderna.
THERE ARE STILL PROBLEMS
However, such tests could be problematic for other types of vaccines, including shots on the whole virus used by several Chinese developers, experts said.
“Where a person is injected with a whole virus-inactivated COVID-19 vaccine … there is a good chance that the person may also have a positive result from IgM antibody tests that are not a peak, ‘Ian Jones, a virologist at the British University, said of reading.
China’s health authority does not explain whether its test is designed to detect antibodies caused by vein proteins or other proteins. The National Health Commission did not respond to a request for comment.
CAN INTEGRATED PERSON ENTER CHINA?
China does not say clearly how it decides to exempt vaccinated people from the requirements for negative antibody tests.
When asked about the subject, one of the embassy staff members in Singapore said that a vaccinated foreigner can submit a vaccination certificate and wait for a response. The Chinese Foreign Ministry declined to comment.
IS USING A VACATION PASS AN OPTION?
At the G20 summit in November, Chinese President Xi Jinping proposed a global mechanism for mutual recognition of health certificates, including nucleic acid tests.
Experts hope China will consider using a vaccine passport to replace the antibody test.
“A vaccination passport will make the trip to China much less difficult,” said Huang Yanzhong, a health expert on the U.S. Council on Foreign Relations’ brainstorming session.
“As Western countries gain herd immunity through mass vaccination, they will begin to open their borders … If China has such strict testing requirements, it will lose its airline, hotel and tourism industry.”
The WHO remains cautious: last week it refrained from advising that global travel is subject to such evidence, citing ‘critical unknowns’ on how effectively the tests limit the spread and also its limited availability.
Reporting by Roxanne Liu and; Yew Lun Tian in Beijing; Edited by Miyoung Kim and Clarence Fernandez