CAPE TOWN- Findings from a seroprevalence survey of hundreds of thousands of people across England suggest there may be a decline in the levels of immunity to Covid-19.
Led by Imperial College London, the study conducted a home-based testing approach to survey the extent of antibody positivity in the population. More than 365,000 volunteers in England took the test between 20 June and 28 September and scientists of the study found that antibody prevalence declined from 6.0% to 4.8% and then 4.4% over the three months.
Seroprevalence surveys uses antibody tests to estimate the percentage of people in a population who have antibodies against Covid-19. The results of the survey could help scientists estimate how many people may have been previously infected with the virus.
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The findings from the Real Time Assessment of Community Transmission (REACT) observed a downward trend in all areas of the country and age groups, but not in health workers, which could indicate repeated or higher initial exposure to the virus.
The decline was largest in people above the age of 75 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.
Director of the programme at Imperial Professor Paul Elliott, said the study found there was 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. 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,” he said.
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