Commuters wearing face masks or blankets due to the COVID-19 pandemic, walk past a London Underground at Victoria Station, during the ‘rus hour’ evening in central London on September 23, 2020 .
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LONDON – Antibodies to the coronavirus are dropping as people recover from the disease, a major British study finds, which could deal a blow to those pushing for so-called herd immunity.
Researchers at Imperial College London screened 365,000 people in England in three rounds of tests between June 20 and September 28.
Analysis of home finger prick tests found that, rather than building immunity over time, the number of people with antibodies capable of fighting Covid-19 has declined by around 26% over the course of time. the study period.
The REACT-2 study, which has not yet been peer reviewed, found that 6% of those tested had antibodies to the virus when UK lockdown measures were rolled out. relaxed during the summer. However, by the start of the second wave of cases last month, that figure had fallen to 4.4%.
“This very large study showed that the proportion of people with detectable antibodies decreases over time,” said Helen Ward, one of the study’s authors and professor at Imperial College London.
“We don’t yet know if this will put these people at risk of re-infection with the virus that causes COVID-19, but it is essential that everyone continue to follow the advice to reduce the risk to themselves and to others.
What does this mean for collective immunity?
The results suggest that there could be a drop in the level of population immunity in the months following the first wave of the coronavirus outbreak, potentially dashing the hopes of those calling for a controversial herd immune response strategy. .
Herd immunity occurs when a sufficient population is immune to a disease, making it unlikely to spread and protecting the rest of the community, according to the Mayo Clinic. It can be achieved by natural infection – when enough people are exposed to the disease and develop antibodies against it – and by vaccination.
Health experts estimate that around 70% of the population should be vaccinated or have natural antibodies to gain herd immunity.
A man wearing a protective mask, takes shelter from the rain under an umbrella as he walks past Chancery Lane tube station in London on October 21, 2020, as the government considers further lockdown measures to fight against the increase in cases of the novel coronavirus COVID-19.
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Some epidemiologists have suggested that targeting herd immunity would be a better response to the pandemic than lockdown measures. Many others, however, have strongly criticized a strategy that could force vulnerable people to protect themselves at home as the virus spreads through young and healthy people.
Earlier this month, Dr Anthony Fauci, the leading infectious disease specialist in the United States, called calls to let the virus tear America’s people apart unchecked as “absurd” and “dangerous.”
To date, more than 43.5 million people worldwide have contracted the coronavirus, with 1.16 million related deaths, according to data compiled by Johns Hopkins University.
Implications for reinfection
The results of the REACT-2 study showed a downward trend in antibodies in people of all age groups and in all parts of the UK, but not among health workers. The decline was largest among people aged 75 and older, according to the study, while the smallest decline was among people aged 18 to 24.
The researchers found that the decline in prevalent antibodies may initially be rapid, before peaking. They warned that data on this is only starting to emerge.
The study only measured antibodies. The authors said it was not possible to determine whether the loss of antibody positivity would correlate with an individual’s increased risk of re-infection, as it was not clear what contribution T-cell immunity and memory responses played into protective immunity upon reexposure.
T cells are part of the immune system that defends itself against specific foreign pathogens.
Late night drinkers after 10 p.m. in Soho, London, after Prime Minister Boris Johnson announced that from Thursday pubs and restaurants would be subject to a 10 p.m. curfew to tackle the increase in coronavirus cases in England.
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“Our study shows that over time, there is a reduction in the proportion of people who test positive for antibodies,” said Professor Paul Elliott, director of the Community Transmission Real-Time Assessment Program at the ‘Imperial, and one of the study’s authors.
“Testing positive for antibodies does not mean you are immune to COVID-19. We still do not know what level of antibody immunity provides, nor how long this immunity lasts, ”he continued.
“If a person tests positive for antibodies, they should always follow national guidelines, including social distancing measures, take a swab test if they have symptoms, and wear masks if necessary.”
– CNBC Noah Higgins-Dunn contributed to this report.