KYOTO -- As new coronavirus infections continue to set new daily highs, antibody tests show that a vast swath of the global population is yet to acquire antibodies to the virus, a reminder of the challenges facing both governments and healthcare professionals.
In a survey of 61,075 people in Spain, one of the largest epicenters of the early coronavirus outbreak, only 5.0% of the participants were found to have antibodies in a rapid test, and 4.6% in a more detailed one.
That means well over 90% of people in Spain do not have antibodies to protect them in the next wave of infection.
The study was based on a survey carried out between Apr. 27 and May 11 and the results were published in the Lancet magazine on July 6.
The study found that only 19.5% of the Spanish respondents who were tested positive in both rapid and detailed tests had previously taken a polymerase chain reaction test.
A third of those who were found to have antibodies also did not exhibit any symptoms, underlining the sheer challenge of detecting infected people.
Recent research also points to a further complication: infected people may not necessarily acquire immunity.
A study published in Nature magazine in June shows that most people who recovered from coronavirus infections did not have a large amount of antibodies in their blood plasma, with only 1% showing a high concentration of antibodies
But all recovered patients have at least a very small amount of antibodies, pointing to the possibility that a vaccine, if carefully designed, could induce proper antiviral activity.
What about Japan?
A study conducted by the health ministry in collaboration with the Japanese Red Cross Society examined a total of 1,500 samples -- 500 from Tokyo in April, 500 from the northern Tohoku prefectures in April and another 500 consisting of preserved samples from January-March 2019 -- using five different testing kits.
Only one sample from Tokyo showed the presence of antibodies in all five tests. That means one in 500 samples for this year, or just 0.2% of the population in Tokyo, have acquired antibodies.
The results, however, need to be taken with a pinch of salt, because such tests could produce wildly different outcomes depending on where the threshold is drawn for positive or negative determination.
The test results need to be carefully analyzed, ideally with advice from researchers who understand the limitations of the testing kits.
While most of the kits were developed overseas, such as in China, there are also testing systems designed by and familiar to Japanese researchers.
Shinya Yamanaka is director of the Center for iPS Cell Research and Application at Kyoto University. He won the Nobel Prize in physiology or medicine in 2012 for his research on how mature cells can be reprogrammed into pluripotent stem cells that can grow into almost any cell type.