With the government announcing they have vaccinated millions of people against coronavirus, some may be wondering if they already have some immunity.
This week Public Health England released a study which had followed almost 21,000 NHS workers for close to five months.
It found that those who suffered from coronavirus and had symptoms had a 90% chance of avoiding getting Covid-19 over the next five months.
And when people who had caught the virus but had been asymptomatic were taken into account, that number fell to 83% - reports Mirror Online.
And now, the study - dubbed Siren - will now continue to track results to see just how long natural immunity lasts after contracting the disease.
With 3.2million people having officially tested positive for coronavirus in the UK, according to Department of Health data, hundreds of thousands may have caught the bug and acquired immunity without suffering any symptoms.
In the UK, the first cases were confirmed on January 31, 2020 - exactly a month after China reported a cluster of cases.
The first confirmed case of transmission inside the UK was registered in Surrey a further month later on February 28.
But many who experienced cold and flu symptoms in the early part of last year believe they could have been struck down by Covid-19 before a test to confirm was developed and widely available.
And while previously having contracted coronavirus does not grant a free pass to shun restrictions, it can be useful to know.
Professor Susan Hopkins, senior medical adviser at PHE and the Siren study lead, warned: "We now know that most of those who have had the virus, and developed antibodies, are protected from reinfection, but this is not total and we do not yet know how long protection lasts.
"Crucially, we believe people may still be able to pass the virus on.
"This means, even if you believe you already had the disease and are protected, you can be reassured it is highly unlikely you will develop severe infections, but there is still a risk that you could acquire an infection and transmit to others."
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But how do you know if you have had it if you never had a test?
There are some symptoms emerging that suggest you could have previously contracted the disease if you are experiencing them.
The only sure fire way to confirm if you have had Covid-19 is either a positive PCR test or antigen test - which tests for a current infection - or an antibody test, which proves you have previously been infected.
And although there are early indications that there are signs of past infection, some symptoms could be also indicative of other health issues. If you have concerns, you should always seek medical advice from a doctor.
These are the 10 signs that could mean you have previously had Covid-19:
1. Memory loss and brain fog
An unpleasant - and in many cases long term - effect of Covid-19 is experiencing a kind of mental fog.
Many sufferers of long Covid have reported having trouble thinking clearly months after getting over the first part of disease.
On Thursday Labour's Andrew Gwynne said that his memory was "shot to pieces".
The MP explained he began to feel "grotty and run down" in March, went on to display Covid-19 symptoms, and his initial illness lasted for about 12 days although he still feels the effects today.
The MP for Denton and Reddish told the Commons: "My condition is not as severe as it was even just a few months back, there have been real improvements, but it's been a hard slog to get here.
"For the first seven months or so the exhaustion came back frequently and to the point where doing just simple tasks around the house brought me out in massive sweats like I'd run the London Marathon.
"I had lots of dizzy spells, I've never had vertigo before this, and oh the brain fog - in a job where you have to be razor sharp, my short-term memory is shot to pieces.
"I've had to learn to pace myself, trying to push my limits would set me back."
2. Covid tongue
According to Professor Tim Spector more and more people are heading to doctors complaining of issues with their tongue after contracting the disease.
The King's College London epidemiologist, who heads the Covid Symptom Study App, said that the disease seems to cause tongue changes including pain, discolouration, swelling or a strange texture.
Professor Spector tweeted: "Seeing increasing numbers of Covid tongues and strange mouth ulcers.
"If you have a strange symptom or even just headache and fatigue stay at home!"
If you are suffering from tongue issues it could be because you've had Covid-19, or that you've got one of a number of other conditions which can be the result of poor mouth hygiene, smoking or an unhealthy diet.
3. Stomach ache
Some coronavirus patients have suffered stomach aches for weeks after catching the bug.
The American Journal of Gastroenterology published a study suggesting the virus could cause digestive problems such as diarrhoea.
It analysed data from 204 patients in China, discovering that 48.5 per cent of them had stomach issues such as vomiting, abdominal pain or diarrhoea when they were first hospitalised.
This is another symptom which may indicate you've had the coronavirus, but it is also indicative of a large range of other conditions - or simply eaten too much or something that hasn't agreed with you.
4. Laboured breathing
While the horrors acute patients suffer in intensive care wards are well understood, research into the impact seemingly mild cases of Covid-19 can have on lungs is only just beginning.
A lot of people who were asymptomatic to begin with have found themselves struggling to breath in the months since being infected.
If you are finding it hard to catch a breath or if you're breathing more heavily than normal, then you may be suffering from Covid-linked lung damage.
5. Fatigue
After weeks of lockdown in the depths of the winter, it may seem difficult to tell coronavirus linked fatigue with general burnout.
Yet sufferers of this common long Covid symptom compare it more to a 'flatlining' sense of exhaustion than typical tiredness.
The symptom can have a crippling impact on people's lives and turn the simplest of tasks into a huge struggle.
If you've been finding yourself low on energy, then you may be one of 38 per cent of people a World Health Organisation study found had Covid linked fatigue.
6. Hair loss
Although not one of the tell-tale signs we've been told to watch out for during the pandemic, hair loss may indicate you've had the coronavirus.
Doctors have long linked unexpected balding with recovery from fevers.
Enid Child shared a picture of her hair loss months after both her and her son tested positive for coronavirus.
The grandmother-of-four, from Pencoe, originally fell ill in mid September, and tested positive for the virus days after.
But it was not until she was referred to her doctor in November that she learnt her hair loss was linked to Covid-19, usually emerging in patients months after their diagnosis.
The 61-year-old said: "The photo I posted was one morning's brush worth.
"That's why I bagged it - I was going to my doctors to get my first lot of bloods to check my iron levels and the rest because my iron levels had dropped. My practice nurse was quite shocked when she saw me.
"She asked does it come out voluntarily. I just put my hand up - by then my hair was waist-length - and ran my hand through my hair and I got another handful.
She said 'I think you better speak to a doctor'.
"The doctor phoned me that afternoon and that was when it was confirmed it was an effect of long Covid."
She added: "My hair has gone really really thin. Yes it still covers my scalp and things but I have lost an awful lot of hair."
7. Eye infections
This symptom is a relatively rare one, but still thought to impact around 3% of the millions of people who've had the coronavirus.
Doctors warned eye infections may be another sign of Covid-19.
Chelsey Earnest, a nurse at the Life Care Centre in Washington, said that red eyes are the ‘single most important’ sign that patients have COVID-19.
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Speaking to CNN she explained: “They have, like...allergy eyes.
"The white part of the eye is not red. It's more like they have red eye shadow on the outside of their eyes.”
Other people have reported symptoms like conjunctivitis.
8. Hearing loss and tinnitus
In November a study was published which showed many people suffered from hearing loss for months after catching the bug.
Researchers from Anglia Ruskin University looked at the hearing problems affecting Covid-19 patients, both in the short and long term.
In the study, the team analysed 3,103 Covid-19 patients with tinnitus - a condition that causes a constant ringing or buzzing in the ears.
The analysis revealed that 40 per cent of the participants experienced a worsening of their tinnitus amid their Covid-19 infection.
And while the majority of participants had pre-existing tinnitus, a small number reported that their conditions as initially triggered by developing Covid-19 symptoms.
9. Anxiety and insomnia
Another symptom that is not the easiest one to spot - given the mental strain many are under each day at the moment - but researchers believe Covid-19 can lead to anxiety, depression and insomnia.
Scientists from the University of Oxford analysed electronic health records of 69 million people in the USA, including over 62,000 Covid-19 patients.
Their analysis revealed that in the three months following a positive Covid-19 test, one in five survivors were found to get a diagnosis of anxiety, depression or insomnia for the first time.
That’s about twice as likely as for people without Covid-19, according to the researchers.
10. Dizziness
Another emerging sign of long Covid, and one which seems to appear commonly in previously asymptomatic patients, is dizziness.
Feeling suddenly wobbly or unsteady on your feet may be a sign you've had the virus.
Dean Dobson was off for work for months due to a particularly bad case of long Covid.
He said: “It's the worst thing I've ever had to experience in my life.
“At the end of February I was at work and I just started getting dizzy, unsteady on my feet, being sick, struggling to breathe.
“I went to the hospital and the doctor who examined me mentioned that people were panicking about coronavirus as it was first hitting the world about that time.
"But he said it was an upper respiratory infection and I was sent home to rest.”
