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Coronavirus antibodies lower after an infection, examine outcomes present, elevating questions on herd immunity

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Commuters wearing a face mask or covering due to the COVID-19 pandemic will walk past a London Underground station during the evening rus hour in central London on 23 September 2020.

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LONDON – Antibodies to the coronavirus decline as people recover from the disease. This emerges from the results of a large UK study that may deal a blow to those pushing for so-called herd immunity.

Researchers from Imperial College London examined 365,000 people in England in three rounds of tests between June 20 and September 28.

Analysis of fingerprint tests performed at home found that the number of people with antibodies that can fight Covid-19 decreased by about 26% over the study period, rather than building immunity over time.

The REACT-2 study, which has not yet been peer-reviewed, found that 6% of people tested had antibodies to the virus when UK lockdown measures were eased over the summer. However, at the start of the second wave of falls last month, that number had dropped to 4.4%.

"This very large study showed that the percentage of people with detectable antibodies decreased over time," said Helen Ward, one of the study's authors and a professor at Imperial College London.

"We don't yet know if this puts these people at risk of re-infection with the virus that is causing COVID-19, but it's important that everyone keep following the directions to reduce the risk to themselves and others. "

What does this mean for herd immunity?

The results suggest that population immunity may decline in the months following the first wave of the coronavirus epidemic, potentially destroying the hopes of those calling for a controversial strategy to combat herd immunity.

According to the Mayo Clinic, herd immunity occurs when enough populations are immune to a disease that it is unlikely to spread and protect the rest of the community. This can be done through natural infections – when enough people are exposed to the disease and develop antibodies to it – and through vaccination.

Health experts estimate that around 70% of the population would need to be vaccinated or have natural antibodies in order to achieve herd immunity.

A man wearing a protective face mask protects himself from the rain under an umbrella as he walks past Chancery Lane Underground Station in London on October 21, 2020. The government is considering further lockdown measures to combat the surge in novel coronavirus-COVID-19 cases.

JUSTIN TALLIS | AFP via Getty Images

Some epidemiologists have suggested that pursuing herd immunity would be a better response to the pandemic than lockdown measures. However, many others have harshly criticized a strategy whereby vulnerable people must provide protection at home while the virus spreads through young and healthy people.

Earlier this month, Dr. Anthony Fauci, the leading infectious disease expert in the US, calls for the virus to penetrate uncontrollably through the US population as "nonsense" and "dangerous".

To date, more than 43.5 million people worldwide have contracted the coronavirus, with 1.16 million deaths, according to data from Johns Hopkins University.

Implications for Reinfection

The REACT-2 study results showed a downward trend in antibodies in people of all ages and in all areas of the UK, but not in health care workers. The largest decrease was seen in people aged 75 and over, while the smallest decrease was seen in people aged 18 to 24.

The researchers found that the decline in predominant antibodies before the plateau can be rapid at first. They warned that data on this was only now emerging.

Only antibodies were measured in the study. The authors said it was not possible to determine whether the loss of antibody positivity would correlate with an increased risk of re-infecting an individual, as it was not clear what contribution T cell immunity and memory responses made to protective immunity during re-infection Exposure played.

T cells are part of the immune system that defends itself against certain foreign pathogens.

Late night drinkers after 10 p.m. in Soho, London after Prime Minister Boris Johnson announced that pubs and restaurants will have a 10 p.m. curfew from Thursday to combat the surge in coronavirus cases in England.

Yui Mok – PA Pictures | PA pictures | Getty Images

"Our study shows that the percentage of people who test positive for antibodies decreases over time," said Professor Paul Elliott, director of Imperial's Real-Time Assessment of Community Data Transmission Program and one of the study's authors.

"Positive testing for antibodies doesn't mean you are immune to COVID-19. It remains unclear how much immunity antibodies offer or how long that immunity lasts," he continued.

"If someone tests positive for antibodies, they must continue to follow national guidelines, including social distancing, get a swab test if they have symptoms, and wear face-covering if necessary."

– CNBC's Noah Higgins-Dunn contributed to this report.

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Steven Gregory