How long does coronavirus immunity REALLY last? 82-year-old man who recovered from the disease is struck down again just 10 days later with the SAME symptoms

An 82-year-old man who spent four weeks in intensive care with Covid-19 was struck down by the virus again just 10 days after recovering.  
The unidentified man went to an emergency department at Massachusetts General Hospital after suffering from a high fever for a week. He tested positive for Covid-19 and then his condition rapidly worsened while he was in hospital.  
Doctors managed to save his life with a lengthy stay on a ventilator but he fell sick again less than a fortnight later, despite testing negative twice before being discharged. 
The man's case is one of many that raises questions about the type of immunity people build up against Covid-19, and how long it really takes to be cleared from the body. 
Medics title their article 'A case report of possible novel coronavirus 2019 reinfection' and discussed how it was possible that the man recovered and tested negative but fell ill again.
Experts are still not sure whether people can catch the coronavirus twice and they are increasingly beginning to believe protection may only be short-lived.
Other coronaviruses that cause the common cold do not produce permanent immunity and people can catch them multiple times, and the same may be true of Covid-19.  
Reports from around the world have claimed to see patients fall ill with the disease more than once, but there is little proof they are reinfections. A high profile group of cases in South Korea turned out to have been false positive results when patients were retested.
Doctors at Massachusetts General Hospital (pictured) revealed the case of the old man who, against all odds, managed to beat the virus twice despite ending up in intensive care both times (Stock image of the hospitals - the patient pictured is not the patient in the report)
Doctors at Massachusetts General Hospital (pictured) revealed the case of the old man who, against all odds, managed to beat the virus twice despite ending up in intensive care both times (Stock image of the hospitals - the patient pictured is not the patient in the report)

The report, published in The American Journal of Emergency Medicine, detailed the case of the unnamed 82-year-old this month. 
The man was already seriously ill before he caught coronavirus, suffering from Parkinson's, diabetes, chronic kidney disease and high blood pressure.
All of these - and his old age - put him in the highest possible risk category of dying from Covid-19. But doctors managed to save him.

He appeared in the emergency department of the hospital complaining of a fever and shortness of breath for a week.
A chest X-ray and examination of his blood oxygen levels led doctors to believe he had Covid-19 and a swab test confirmed his diagnosis.
While in A&E the man's lungs began to fail so he was put on a ventilator and rushed to intensive care, where he then spent 28 days recovering.
He spent a total of 39 days - five-and-a-half weeks - in hospital before being discharged to rehab.
After two negative coronavirus tests he was allowed to leave the ward and was breathing on his own.
But just 10 days later the man reappeared in the emergency department - again with a fever and struggling to breathe.
Another chest X-ray showed signs of Covid-19 infection in his lungs again, and a swab test again confirmed he was carrying the virus. 
This time he and his family had asked doctors not to put him on a ventilator and not to resuscitate him if his heart stopped, but he was admitted to intensive care again.
In the ITU he went into shock and his kidneys failed - but again he survived, recovered and was sent back to a normal ward after a week.
After testing negative for coronavirus a further two times, he was discharged from the hospital for a second time after 15 days and is since believed to have recovered.
His medics said that, rather than getting infected twice, it's likely he never fully recovered the first time and that tests weren't sensitive enough to notice he was still carrying the virus.
The doctors, led by Dr Nicole Duggan, said: 'Many viruses demonstrate prolonged presence of genetic material in a host even after clearance of the live virus and symptomatic resolution. 
'Thus, detection of genetic material by [swab test] alone does not necessarily correlate with the active infection or infectivity.
'Observational data suggest SARS-CoV-2 viral shedding may last 20-22 days after symptom onset on average with some outlying cases exhibiting shedding as long as 44 days.'
They said that in one 71-year-old woman, a study had found she continued to test positive for Covid-19 five weeks after her symptoms disappeared.
Because the virus was only first discovered in December, scientists have not had the opportunity to work out how it affects people in the long-term. 
In one study done by the University of Amsterdam, researchers suggested the coronavirus may act in the same way as other coronaviruses that cause common colds and other infections. 
The researchers followed 10 volunteers for 35 years and tested them every month for four seasonal and weaker coronaviruses named NL63, 229E, OC43, and HKU1.
Those viruses are much more common and cause mild illnesses similar to the common cold.
They found those who had been infected with the strains — from the same family as SARS-CoV-2, the type that causes Covid-19 — had 'an alarmingly short duration of protective immunity'.  
Levels of antibodies, substances stored by the immune system to allow the body to fight off invaders in the future, dropped by 50 per cent after half a year and vanished completely after four years. 
By studying how people recover from viruses from the same family as the one that causes Covid-19, the scientists say their research is the most comprehensive look at how immunity might work for the disease that emerged in China last year.
Writing in the study, which has not yet been published in a scientific journal or reviewed by other scientists, the scientists said: 'The seasonal coronaviruses are the most representative virus group from which to conclude general coronavirus characteristics, particularly common denominators like dynamics of immunity and susceptibility to reinfection.  
'In conclusion, seasonal human coronaviruses have little in common, apart from causing common cold. 
'Still, they all seem to induce a short-lasting immunity with rapid loss of antibodies. This may well be a general denominator for human coronaviruses.' 

They added: 'Our study also shows that herd immunity may be challenging due to rapid loss of protective immunity. 
'It was recently suggested that recovered individuals should receive a so-called "immunity passport", which would allow them to relax social distancing measures and provide governments with data on herd immunity levels in the population.
'However, as protective immunity may be lost by six months post infection, the prospect of reaching functional herd immunity by natural infection seems very unlikely.'  
A study by the University of Melbourne discovered that antibody immunity - which many had pinned their hopes on - only seems to develop in 'modest' amounts in Covid-19 patients.
Tests on 41 people in Australia found that only three of them developed a strong enough antibody immune response that they could block half of the viruses if they got into the body again.
On average, the immune system's antibodies were only able to block 14.1 per cent of the coronaviruses if someone was exposed to the illness a second time, making it likely that someone could get ill again. 
Antibodies are only one type of immunity but they are usually the fastest-acting and what is needed to prevent illness.
Other types of immunity — such as that produced by white blood cells called T cells — may make disease less severe but not stop it completely. The Australian researchers said T cells appeared to be a better sign of immunity than antibodies.
The study was promising in that it showed coronavirus infection did stimulate the production of multiple types of immunity, including T cells and another form of white blood cell called B cells.  
These could be 'boosted', one scientist suggested, if they weren't produced in large enough quantities naturally.
The Australian researchers warned a vaccine is 'urgently needed' because having had Covid-19 once might not protect people from getting it again.  
Other more promising research, however, has found that monkeys are unable to be reinfected with the virus in laboratory experiments.
Researchers in China infected rhesus monkeys with coronavirus, allowed them to recover, and then re-exposed them to the virus 28 days after the initial infection.
However, the monkeys were seen to have appeared to have developed protection against the infection and did not succumb a second time.
This, the team argued, would suggest that patients who appeared to become 'reinfected' with coronavirus merely had not fully overcome the initial infection. 
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