Antibodies disappear quickly
The largest study on antibodies to coronavirus has been completed
Scientists from the UK conducted mass testing for antibodies to coronavirus among residents of the country. It turned out that over time, the proportion of the population with antibodies does not increase, but, on the contrary, decreases, and those who suffered from COVID-19 asymptomatically lose antibodies the fastest. The results of the study are published as a preprint on the website of Imperial College London (Ward et al., Declining prevalence of antibody positivity to SARS-CoV-2: a community study of 365,000 adults).
The study called REACT (Real Time Assessment of Community Transmission) involved 365 thousand randomly selected adults of different ages, who, from June 20 to September 28, 2020, conducted rapid testing for antibodies to the SARS-CoV-2 coronavirus three times at home using a blood sample from a finger.
The results showed that in the three months during which the testing was carried out, the prevalence of viral antibodies among residents of England decreased by more than a quarter – from six to 4.4 percent.
The decline coincides with a sharp drop in the rate of spread of the virus in the country after months of quarantine measures. According to the authors, this suggests that people's immune response to COVID-19 is declining quite rapidly.
Antibodies are especially rapidly lost by those who had an asymptomatic disease, as well as older people: in people from the age group of 18-24 years, antibodies persisted much longer than in the group of 75 years and older.
In people who did not report a history of COVID-19, the decrease between the first and third rounds of testing was 64 percent, compared with 22.3 percent in people whose infection was confirmed by laboratory.
"This very large study showed that the proportion of people with detectable antibodies decreases over time," the press release says. The words of the first author of the article Professor Helen Ward (Helen Ward).
"It remains unclear to the end what level of immunity the antibodies provide and how long this immunity persists," continues the head of the study Paul Elliott (Paul Elliott). – If someone tests positive for antibodies, it does not mean that they are immune to COVID-19. He must still follow national guidelines, including social distancing measures, take a smear if he has symptoms, and wear a face mask."
The authors note that the tendency to decrease the level of antibodies is observed in all regions of the country and age groups. The exception is medical workers whose number of antibodies has not changed over time. According to scientists, this is due to repeated contacts or higher initial exposure to the virus. The study also says that residents of London had the highest proportion of positive tests – about twice the national average.
The main result of the study, according to the authors, is that collective immunity decreases over time, not increases. At the same time, a positive result for antibodies at the moment does not mean that immunity to COVID-19 will remain at the next contact with the virus. Thus, the researchers conclude, there is a risk of re-infection.
Scientists from the REACT project continue their research in order to monitor the level of current infection, testing more than 150 thousand people every month.
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