COVID-19 antibodies drop in UK study
October 27, 2020
In tests carried out on 365,104 people in England from June to September, the number of people testing positive for coronavirus antibodies dropped by 26.5%.
The study, known as REACT, was led by Imperial College London. It used a finger-prick test to check for antibodies in the blood. Antibodies show that a person has been previously infected with a virus, and in this case, the virus that causes COVID-19.
Results from the group of randomly selected volunteers showed a "downward trend in all areas of the country and age groups."
In a preprint paper, the scientists said the "data suggest the possibility of decreasing population immunity and increasing risk of reinfection as detectable antibodies decline in the population."
The study has yet to be peer reviewed or verified by other scientists and COVID-19 experts.
Professor Paul Elliott, a co-author of the paper, said the connection between coronavirus antibodies and immunity against reinfection "remains unclear."
The test and its results
Three rounds of tests were carried out at 12, 18 and 24 weeks after the first peak of SARS-CoV-2 infections in England.
Once registered for the study, participants were sent a Lateral Flow Test kit, which they self-administered to provide a blood sample from a finger prick.
They then answered a questionnaire. The scientists say the participants were not "blind" to their results and, as a result, may have added bias to their answers. But the study authors also say that "should not have affected our observation of declining prevalence [of coronavirus antibodies] over time."
Results showed a decline between rounds one and three in all age groups. The highest prevalence of a positive result and smallest overall decline in positivity were in the youngest age group of 18-24 years.
The lowest prevalence and largest decline in antibodies were in the oldest group of 75 years and above. There was no change in antibody positivity between rounds one and three in health care workers.
"During any antibody response to an acute pathogen, some level of antibody waning in the months following infection is expected as short-lived plasma cells die," the study authors wrote. "Low levels of affinity-matured antibody usually continues to be produced by long-lived plasma cells and may be sufficient to maintain levels of antibody that confer immunity."
A series of studies
REACT, or Real-time Assessment of Community Transmission, is a series of studies.
The first, REACT1, involves antigen (swab) tests, with the aim of examining how widely the virus has spread and how many people are currently infected with it.
REACT2 is assessing different antibody tests to see how accurate they are and how easily people can use them at home.
Antigens are viruses or bacteria that can cause an immune response in the body. Antibodies are then produced by the body as a response to an infection.