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Herd immunity assumptions challenged by latest research

There is a growing body of evidence that immunity to COVID-19 is short lived, writes MedicalBrief. The latest study, from the UK, found levels of antibodies peaked about three weeks after the onset of symptoms then swiftly declined.

The latest research suggests that people who have recovered from COVID-19 may lose their immunity to the disease within months, and the virus could re-infect people year after year, like common colds.

The Guardian reports that in the first longitudinal study of its kind, scientists analysed the immune response of more than 90 patients and healthcare workers at Guys and St Thomas NHS Foundation Trust and found levels of antibodies that can destroy the virus peaked about three weeks after the onset of symptoms then swiftly declined.

Blood tests revealed that while 60% of people marshalled a “potent” antibody response at the height of their battle with the virus, only 17% retained the same potency three months later. Antibody levels fell as much as 23-fold over the period. In some cases, they became undetectable.

“People are producing a reasonable antibody response to the virus, but it’s waning over a short period of time and depending on how high your peak is, that determines how long the antibodies are staying around,” said Dr Katie Doores, lead author on the study at Kings College London.

The study has implications for the development of a vaccine, and for the pursuit of “herd immunity” in the community over time.

The report says the immune system has multiple ways to fight the coronavirus but if antibodies are the main line of defence, the findings suggested people could become re-infected in seasonal waves and that vaccines may not protect them for long.

The King’s College study is the first to have monitored antibody levels in patients and hospital workers for three months after symptoms emerged. The scientists drew on test results from 65 patients and six healthcare workers who tested positive for the virus, and a further 31 staff who volunteered to have regular antibody tests between March and June.

The report says the study, which has been submitted to a journal but has yet to be peer-reviewed, found that antibody levels rose higher and lasted longer in patients who were severe cases. This may be because the patients have more virus and churn out more antibodies to fight the infection.

Professor Jonathan Heeney, a virologist at the University of Cambridge, said the study confirmed a growing body of evidence that immunity to COVID-19 is short-lived. “Most importantly, it puts another nail in the coffin of the dangerous concept of herd immunity,” he said.

“I cannot underscore how important it is that the public understands that getting infected by this virus is not a good thing. Some of the public, especially the youth, have become somewhat cavalier about getting infected, thinking that they would contribute to herd immunity. Not only will they place themselves at risk, and others, by getting infected, and losing immunity, they may even put themselves at greater risk of more severe lung disease if they get infected again in the years to come.”

But Professor Arne Akbar, an immunologist at University College London, said antibodies are only part of the story. There is growing evidence, he said, that T cells produced to fight common colds can protect people as well. Those patients who fight the virus with T cells may not need to churn out high levels of antibodies, he added.

Abstract
Antibody (Ab) responses to SARS-CoV-2 can be detected in most infected individuals 10-15 days following the onset of COVID-19 symptoms. However, due to the recent emergence of this virus in the human population it is not yet known how long these Ab responses will be maintained or whether they will provide protection from re-infection. Using sequential serum samples collected up to 94 days post onset of symptoms (POS) from 65 RT-qPCR confirmed SARS-CoV-2-infected individuals, we show seroconversion in >95% of cases and neutralizing antibody (nAb) responses when sampled beyond 8 days POS. We demonstrate that the magnitude of the nAb response is dependent upon the disease severity, but this does not affect the kinetics of the nAb response. Declining nAb titres were observed during the follow up period. Whilst some individuals with high peak ID50 (>10,000) maintained titres >1,000 at >60 days POS, some with lower peak ID50 had titres approaching baseline within the follow up period. A similar decline in nAb titres was also observed in a cohort of seropositive healthcare workers from Guy′s and St Thomas′ Hospitals. We suggest that this transient nAb response is a feature shared by both a SARS-CoV-2 infection that causes low disease severity and the circulating seasonal coronaviruses that are associated with common colds. This study has important implications when considering widespread serological testing, Ab protection against re-infection with SARS-CoV-2 and the durability of vaccine protection.

Authors
Jeffrey Seow, Carl Graham, Blair Merrick, Sam Acors, Kathryn JA Steel, Oliver Hemmings, Aoife O’Bryne, Neophytos Kouphou, Suzanne Pickering, Rui Galao, Gilberto Betancor, Harry D Wilson, Adrian W Signell, Helena Winstone, Clair Kerridge, Nigel Temperton, Luke Snell, Karen Bisnauthsing, Amelia Moore, Adrian Green, Lauren Martinez, Brielle Stokes, Johanna Honey, Alba Izquierdo-Barras, Gill Arbane, Amita Patel, Lorcan O’Connell, Geraldine O’Hara, Eithne MacMahon, Sam Douthwaite, Gaia Nebbia, Rahul Batra, Rocio Martinez-Nunez, Jonathan D Edgeworth, Stuart JD Neil, Michael H Malin, Kathie Doores

 

A top New York doctor is quoted as saying, meanwhile, that herd immunity wasn’t a factor in decreasing the number of cases of coronavirus in New York City, says a New York Post report. Mayor Bill de Blasio and Dr Jay Varma attributed the city’s good numbers to everything but herd immunity – including social distancing, good hygiene and an increase in testing and tracing.

“I think that herd immunity is a very unlikely explanation for this because we know the vast major of New Yorkers actually weren’t infected, so we’re not nearly at a level where we would expect that immunity would play a major role in decreasing transmission,” Varma, the city’s senior adviser for public health, is quoted in the report as saying. “There’s still far too many New Yorkers that are susceptible,” he added.

 

New York is expecting anti-bodies and herd immunity to play a role in the anticipated "second wave" of COVID-19.

At a clinic in Corona, a working-class neighbourhood in Queens, more than 68% of people tested positive for antibodies to the new coronavirus. At another clinic in Jackson Heights, Queens, that number was 56%. But at a clinic in Cobble Hill, a mostly white and wealthy neighbourhood in Brooklyn, only 13% of people tested positive for antibodies. The News York Times reports that as it has swept through New York, the coronavirus has exposed stark inequalities in nearly every aspect of city life, from who has been most affected to how the health care system cared for those patients. Many lower-income neighbourhoods, where Black and Latino residents make up a large part of the population, were hard hit, while many wealthy neighbourhoods suffered much less.

But now, as the city braces for a possible second wave of the virus, some of those vulnerabilities may flip, with the affluent neighbourhoods becoming most at risk of a surge. According to antibody test results from CityMD that were shared with The New York Times, some neighbourhoods were so exposed to the virus during the peak of the epidemic in March and April that they might have some protection during a second wave.

“Some communities might have herd immunity,” said Dr Daniel Frogel, a senior vice president for operations at CityMD, which plays a key role in the city’s testing programme.

While stopping short of predicting that those neighbourhoods would be protected against a major new outbreak of the virus – phenomenon known as herd immunity – several epidemiologists said that the different levels of antibody prevalence across the city are likely to play a role in what happens next, assuming that antibodies do in fact offer significant protection against future infection.
“In the future, the infection rate should really be lower in minority communities,” said Kitaw Demissie, an epidemiologist and the dean of the School of Public Health at SUNY Downstate Medical Centre in Brooklyn.

Dr Ted Long, the executive director of the city’s contact-tracing programme, said that while much remained unknown about the strength and duration of the protection that antibodies offer, he was hopeful that hard-hit communities like Corona would have some degree of protection because of their high rate of positive tests. “We hope that that will confer greater herd immunity,” he said.

[link url="https://www.theguardian.com/world/2020/jul/12/immunity-to-covid-19-could-be-lost-in-months-uk-study-suggests"]Full report in The Guardian[/link]

 

[link url="https://www.medrxiv.org/content/10.1101/2020.07.09.20148429v1"]medRxiv abstract[/link]

 

[link url="https://nypost.com/2020/07/10/herd-immunity-played-no-role-in-decreasing-nyc-covid-19-cases-doctor/"]Full New York Post report[/link]

 

[link url="https://www.nytimes.com/2020/07/09/nyregion/nyc-coronavirus-antibodies.html"]Full report in The New York Times[/link]

 

 

See also
[link url="https://www.medicalbrief.co.za/archives/covid-19-herd-immunity-may-be-unachievable-spanish-study-of-61000-people/"]COVID-19 herd immunity may be unachievable — Spanish study of 61,000 people[/link]

[link url="https://www.medicalbrief.co.za/archives/what-policy-makers-need-to-know-about-protective-immunity-the-lancet-commentary/"]What policy makers need to know about protective immunity — The Lancet commentary[/link]

[link url="https://www.medicalbrief.co.za/archives/norway-and-sweden-re-assess-their-initial-covid-19-lockdown-strategies/"]Norway and Sweden re-assess their initial COVID-19 lockdown strategies[/link]

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