Ten thousand healthcare workers have signed up to take part in a Government study which aims to solve the mystery of whether people can get reinfected with Covid-19.
Public Health England researchers will follow volunteers for at least a year, regularly swabbing them for the virus and taking blood samples to search for antibodies.
Participants are a mix of frontline NHS staff of all ages from hospitals dotted across England, many of whom will have already had coronavirus and recovered.
Recruitment in Scotland, Wales and Northern Ireland will begin in the coming weeks and PHE told MailOnline today it hopes to eventually recruit 100,000 volunteers.
Preliminary results from the study, known as SIREN (SARS-CoV-2 Immunity and REinfection EvaluatioN) are expected before the winter — when experts fear Britain will be hit by a second wave.
There is currently no scientific consensus about how long natural immunity against Covid-19 lasts because the disease hasn’t been around long enough.
The European Centre for Disease Control estimates survivors are protected for up to a year, depending on their age and how good their immune system is. This is in line with common colds and seasonal flu, which is why people are urged to get a new influenza jab every year.
But the Centre for Disease Control (CDC) in the US says its research indicates that immunity lasts just three months, the same as other human coronaviruses.
Scientists need to iron out the burning question of Covid immunity to inform public health policies — like who is safe to go back to work and which vulnerable groups must continue to shield.
It also would mean that any protection from a vaccine may not be very long lasting and a jab may need to be reformulated every year.
Professor Susan Hopkins, an epidemiologist at PHE who is leading the study, said said: ‘Every day we learn more and more about the impacts of becoming infected with Covid-19.
‘But we don’t know if you can get it again, if you can pass it on, or if you develop immunity. We urgently need to find out the answers to these questions as rapidly as possible.
‘I can’t overstate how grateful we are to the ten thousand NHS doctors, nurses, cleaners and porters who have signed up so far to help improve our knowledge about this new infection.’
Health minister Lord Bethell added: ‘Understanding our body’s response to Covid-19 is a critical step in beating this horrible virus.
‘That’s why this clinical study, one of the largest in the world, is so important. It will help us understand the mystery of our antibody response to Covid-19.’
The biggest UK study into Covid immunity was carried out by King’s College London and published last month.
Scientists looked at the immune response of more than 90 patients and healthcare workers at Guy’s and St Thomas’ NHS foundation trust. They found antibody levels peaked three weeks after symptoms emerged and then declined.
The findings suggest that, like the common cold and flu, the virus could infect people on an annual basis. This undermines ideas that herd immunity could be a way of defeating the virus.
Lead author Dr Katie Doores told the Guardian: ‘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.’
This means antibody levels were highest and lasted longest in patients who had the most severe cases.
It also would mean that any protection from a vaccine may not be very long lasting and the vaccine may need to be reformulated every year.
But there remains a chance that even if antibody levels drop, the body could fight off the virus a second time using T-cells.
It comes as another study found more than half of hospitalised coronavirus patients given heart scans worldwide were found to have abnormalities.
Some 55 per cent of 1,261 patients from 69 countries had abnormal changes to the way their heart was pumping, with around one in seven showing evidence of severe dysfunction, the study, which was funded by the British Heart Foundation, found.
The majority of patients had never been diagnosed with heart problems before, leading scientists to conclude that Covid-19 may seriously affect the heart.
Cases of reinfection have been cropping up in countries around the world, but experts have tended to blame inaccurate test results or lengthy illness.
Some say it is not uncommon for parts of viruses to keep circulating even after recovery.
A scientific paper entitled ‘A case report of possible novel coronavirus 2019 reinfection’ was published in the US recently describing the case of an 82-year-old man who was hospitalised twice by the virus.
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.
He again needed intensive care and recovered for a second time, although the state of his health afterwards was not revealed.
Medics discussed in the The American Journal of Emergency Medicine how it was possible that the man recovered and tested negative but fell ill again.
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.’