Antibody tests carried out in England have showed that the number of people with antibody response to the novel coronavirus that causes COVID-19 is dropping over time, according to study released Tuesday by the Imperial College London.
The Real Time Assessment of Community Transmission (REACT) study, led by the college, is using finger-prick testing to detect coronavirus antibodies in the blood.
Researchers then analyzed the results of these tests carried out at home between June 20 and Sept. 28, which involved more than 365,000 people in England.
They found that the number of people with antibodies dropped by 26.5 percent across the study period.
The latest results included findings from three rounds of testing carried out over a three-month period, and antibody prevalence declined from 6 percent to 4.8 percent and then 4.4 percent over the three months.
The decline was largest in people aged 75 and above compared to younger people, and also in people with suspected rather than confirmed infection, indicating that the antibody response varies by age and with the severity of illness, according to the study.
"Our study shows that over time there is a reduction in the proportion of people testing positive for antibodies. Testing positive for antibodies does not mean you are immune to COVID-19. It remains unclear what level of immunity antibodies provide, or for how long this immunity lasts," said professor Paul Elliott, director of the program at the college.
"If someone tests positive for antibodies, they still need to follow national guidelines including social distancing measures, getting a swab test if they have symptoms and wearing face coverings where required," Elliott said.
The study result dealt a heavy blow to the hope of the so called "herd immunity" proposed by some scientists as an alternative to lockdowns in fighting the coronavirus pandemic, Sky News reported.
Professor Helen Ward, one of the researchers, said the new results strongly suggest that herd immunity is unachievable.
"When you think 95 people out of 100 are still likely to be susceptible, we are a long, long way from anything resembling population level protection against onward transmission," she was quoted by Sky News as saying.
"It's not something you can use as a strategy for infection control (for COVID-19) in the population," she said.
To bring life back to normal, countries, such as Britain, China, Russia and the United States, are racing against time to develop coronavirus vaccines.
