According to Britain's most extensive research released on Tuesday, asymptomatic coronavirus sufferers tend to lose observable antibodies earlier than individuals who have shown Covid-19 symptoms.
The results of Imperial College London and market analysis company Ipsos Mori also show that in 18-24 year-olds, the depletion of antibodies was slower relative to those aged 75 and over.
Scientists also have tracked antibody levels in the British population following the first wave of COVID-19 infections in March and April.
Overall, samples from hundreds of thousands of individuals across England found that the prevalence of virus antibodies dropped by more than a tenth.
Declining Antibodies
The report, commissioned by the British government and released by Imperial on Tuesday, implies that people's immune response to Covid-19 declines with time following infection.
The antibodies against the novel coronavirus decreased rapidly throughout the summer also indicated that the defense following infection might not be long-lasting.
James Bethell, junior health minister, said it "a critical piece of research, helping us to understand the nature of Covid-19 antibodies over time".
But scientists concerned warned that something about the long-term antibody reaction of people to the virus remains unclear.
"It remains unclear what level of immunity antibodies provide, or for how long this immunity lasts," said Paul Elliott, of Imperial's School of Public Health.
Between June 20 and September 28, the analysis included 365,000 randomly chosen individuals conducting three rounds of fingerprick checks for coronavirus antibodies at home.
The findings revealed that the number of individuals with antibodies during the approximate three-month span dropped by 26.5 percent.
Scaled up to a national standard, the report noted the proportion of the English population with antibodies drops from 6.0 percent to 4.4 percent.
During a month-long national closure that was eased over the summer, the downturn culminated with the virus's incidence declining sharply across England and the rest of Britain.
No Improvements
However, the analysis showed that the amount of health care staff who tested positive for antibodies did not improve with time, likely indicating repeated or higher initial virus exposure.
Study co-author Helen Ward said the "very broad" research showed that the proportion of people with measurable antibodies decreases over time.
"On the balance of evidence I would say, with what we know for other coronaviruses, it would look as if immunity declines away at the same rate as antibodies decline away, and that this is an indication of waning immunity at the population level."
Compared to those who had been asymptomatic and ignorant of their initial infection, those whose COVID-19 was confirmed by a gold standard PCR examination had a less pronounced reduction in antibodies.
The amounts of antibodies seen in healthcare employees, likely due to prolonged exposure to the infection, did not change.
The results of Imperial were published as a pre-print document and have not been peer-reviewed yet.
Barclay said the gradual decline in infection antibodies did not impact vaccine candidates' potency in clinical trials.
"A good vaccine may well be better than natural immunity," she said.
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