A study conducted in England shows that over several months, one type of antibody against COVID-19 became less prevalent among people who had been infected with the disease.
Researchers from Imperial College London sent finger-prick tests to more than 365,000 people across England, selected at random. Data from the tests showed that, initially, 6% of people had an IgG antibody against COVID-19. This is just one type of antibody the human body produces to develop immunity against the virus.
The first round of tests was conducted starting in June. Subsequent rounds conducted had concluded by late September. Results of the later tests showed only 4.4% had the specific antibody.
"This is consistent with evidence that immunity to seasonal coronaviruses declines over 6 to 12 months after infection and emerging data on SARS-CoV-2 that also detected a decrease over time in antibody levels in individuals followed in longitudinal studies," the researchers' report reads.
Other researchers have found that other types of antibodies against coronavirus may last longer than IgG antibodies do.
The scientists found a greater rate of antibody decline among people age 75 and older and among people who only said they suspected they had the virus. The latter indicate that stronger disease symptoms correlate with longer lasting immunity, the researchers said.
The report has not yet been peer reviewed by other scientists.