Immunity to Covid-19 could be lost in months - Politics Forum.org | PoFo

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#15106984
Those who supported herd immunity are responsible for thousands of deaths. There will never be any herd immunity if antibodies disappear after a few months.

Even the idea of a vaccine looks questionable. Those who let the virus spread in the hope of a vaccine (Trump) that may not materialize acted in a very irresponsible manner.

In the end, there may be nothing but non-chemical interventions like testing, tracing and isolation to contain the virus. Countries that have let the virus spread will find it very costly to get it under control.

Immunity to Covid-19 could be lost in months

People who have recovered from Covid-19 may lose their immunity to the disease within months, according to research suggesting the virus could reinfect people year after year, like common colds.

In the first longitudinal study of its kind, scientists analysed the immune response of more than 90 patients and healthcare workers at Guy’s 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 King’s 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 immune system has multiple ways to fight the coronavirus but if antibodies are the main line of defence, the findings suggested people could become reinfected in seasonal waves and that vaccines may not protect them for long.

Infection tends to give you the best-case scenario for an antibody response, so if your infection is giving you antibody levels that wane in two to three months, the vaccine will potentially do the same thing,” said Doores. “People may need boosting and one shot might not be sufficient.”

Early results from the University of Oxford have shown that the coronavirus vaccine it is developing produces lower levels of antibodies in macaques than are seen in humans infected with the virus. While the vaccine appeared to protect the animals from serious infection, they still became infected and may have been able to pass on the virus.

Speaking on Sky News, Prof Robin Shattock of Imperial College London said a competing vaccine developed by his group could be available in the first half of next year if clinical trials go well. But he cautioned there was “no certainty” any of the vaccines in development would work, and said it is still unclear what kind of immune response is needed to prevent infection.

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 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.

There are four other types of coronavirus in widespread circulation, which cause the common cold. “One thing we know about these coronaviruses is that people can get reinfected fairly often,” said Prof Stuart Neil, a co-author on the study. “What that must mean is that the protective immunity people generate doesn’t last very long. It looks like Sars-Cov-2, the virus that causes Covid-19, might be falling into that pattern as well.”

Prof 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 Prof Arne Akbar, an immunologist at UCL, 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.

Shattock said the study was important and indicated that neutralising antibodies rapidly wane. “This certainly suggests that we cannot be confident natural infection will be protective for a significant proportion of individuals, nor certain of the duration of any protection.”

He added: “We would however expect that re-infection would be less severe for any individual as they will still retain immune memory allowing them to more rapidly respond. Nevertheless they could still be a source of onward transmission.

“It does indicate that vaccines need to do better than natural infection, providing consistent responses in the majority of individuals and sustained levels of protective antibodies. Ultimately this may require the use of annual boosting immunisations, particularly for the most vulnerable. This could be delivered alongside annual influenza immunisations.”


Studies in Germany and China have confirmed that there is a marked reduction in antibodies after a few months.
#15106988
The short answer is we don't know.
Even for those diseases that we do develop solid immunity and we have vaccines, etc. Usually, protection is not 100% and people can still get infected if their immune system is a bit down (elderly, pregnancy, drugs that alter the immune system, etc) or if the inoculum is too high (even a healthy person can get infected if they start licking the pustules of a patient with disseminated herpes zoster).
In the end, the truth is likely to be somewhere in the middle, just don't know how far to one side or the other.
The other issue is whether reinfection would be a milder disease, possibly or the same or worse? It seems the main issue with this disease is not the virus itself but the immune system, and it is possible that an immune system that already saw the virus might put a far more robust (and more damaging to the body) reaction that could make the patient sicker.

This is all interesting to talk about and research, but it does not make a difference to our current perils. This is a public health/epidemiology issue at this point, more than a medical one.
#15106992
Disease severity enhances the magnitude of the antibody (Ab) response that correlates with disease severity. Most asymptomatic patients were not able to generate nAb titres >1000, for whom SARS-CoV-2 infection generates only a transient immune response that rapidly declines. The more transient Ab responses in the lower disease severity cases is similar to the immune response to the common cold, which have also been reported to be more transient. In short, if you were hospitalized for Covid-19, the Ab response would last much longer (up to a year) than these asymptomatic patients, who are much younger and somewhat immune to Covid-19 in the first place.

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.
https://www.medrxiv.org/content/10.1101 ... 20148429v1


What percentage of patients have been reinfected?


It was up to 10% in Wuhan.

About 3 to 10 per cent of patients who recovered from Covid-19 tested positive again after being discharged from hospital, doctors in Wuhan have found.

Wang Wei, president of Tongji hospital told CCTV’s prime-time programme that of the 147 recovered patients they studied, only five – or just over 3 per cent – have tested positive in nucleic acid tests again after recovery.

Meanwhile, Life Times, a health news outlet affiliated with People’s Daily, reported this week that quarantine facilities in Wuhan have reported that about 5 to 10 per cent of their recovered patients tested positive again.

https://www.scmp.com/news/china/society ... -later-say
Last edited by ThirdTerm on 13 Jul 2020 07:40, edited 1 time in total.
#15106995
What percentage of patients have been reinfected? I'm asking because the tests have a specificity of around 99%. This means that you could expect (say) 1% of all the positives to actually be false - and as such, they could be "reinfected" (i.e. become actually infected for the first time).
#15106997
This is all interesting to talk about and research, but it does not make a difference to our current perils. This is a public health/epidemiology issue at this point, more than a medical one.


Bingo.

The fact is that beating this disease in both the short and long haul is a simple exercise in cutting exposures. Nothing more.

The public has been inundated with terms that are, to say the least, discrete in meaning. "Herd Immunity" is a good example. The real deal is that because we have neither credible treatments nor the prospect of a working vaccine in the near term, all we can do, and all we have to do, is cut transmission rates.

This is really quite easy. How to dampen the economic consequences of it is not easy. But there are solutions. We need a national strategy. We will not get this from Trump. He does not even see this as a disease.

People on this forum ought to realize that the solution to this disease is not hard. It is being done all over the world. It is necessary to save hundreds of thousands of lives. Waiting for a vaccine or a silver bullet is murder. Believing Trump and most Republican governors is suicide. Stay apart. Wear a mask whenever you are out of your house. Stay at least 6 feet away from everyone else. Wash your hands constantly and use hand sanitizer constantly. Keep kids out of school for now. Wash everything you bring into the house. No rocket science. Just real science.
#15107106
XogGyux wrote:The other issue is whether reinfection would be a milder disease, possibly or the same or worse? It seems the main issue with this disease is not the virus itself but the immune system, and it is possible that an immune system that already saw the virus might put a far more robust (and more damaging to the body) reaction that could make the patient sicker.


The study I cited actually suggests the opposite: a 2nd infection may be worse than the 1st one, especially if organs have been damaged or weakened during the 1st infection, as seems to be the case with numerous patients.

As @ThirdTerm remarks, an asymptomatic infection seems to provide little or no immunity. The degree and lengths of the immunity seems to be proportional to the severity of the infection.

I think there is no way around the fact that antibodies do disappear after a few months. Obviously, there are other factors like the T-cells that can fight an infection, but the fact that antibodies don't last is bad news for vaccines using antibodies.

Drlee wrote:People on this forum ought to realize that the solution to this disease is not hard. It is being done all over the world. It is necessary to save hundreds of thousands of lives. Waiting for a vaccine or a silver bullet is murder. Believing Trump and most Republican governors is suicide. Stay apart. Wear a mask whenever you are out of your house. Stay at least 6 feet away from everyone else. Wash your hands constantly and use hand sanitizer constantly. Keep kids out of school for now. Wash everything you bring into the house. No rocket science. Just real science.


That's really the short of long of it. Trump has been looking for a miracle that will make the virus go away. First it was the warm weather that would make the pandemic go away by April (because comrade Xi told him so), then in was a vaccine that would materialize within a couple of months, then it was hydroxychloloquin, then it was bleach and UV light ... anything that would avoid the president having to do anything about it.

All of these miracle solutions disappear into thin air one by one like a Fata Morgana and governments who pinned their hope on the silver bullets or herd immunity will have to start from scratch being facing with a mountain of infections, to patiently cut the chains of infections by well-proven containment strategies.

I think there is a lot of scope for innovation in containment methods. If we get a rapid low-cost test using saliva people could be tested whenever they have to interact with others. A test returning a result within minutes for less than a dollar could be used before you board a plane or train, or even before you visit a crowded restaurant or go to visit your elderly parents.

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