A new series of lockdowns are now in force in England and most of Scotland, as well as Wales and Northern Ireland.
Here are some of your questions about the roll-out of the vaccination, new international travel rules and school closures.
Questions and answers
My 89-year-old father had the vaccine a week ago. Is it safe to hug him now? From Cheryle LockeMichelle Roberts Health online editor
Lots of people are wondering whether having the vaccine will stop them spreading coronavirus.
We know the vaccine significantly reduces the risk of getting seriously ill with coronavirus. But it is unclear whether it stops people from catching it or passing it on to others.
So it is really important that people continue with social distancing, wearing face coverings and washing their hands, even if they have been immunised.
It's also worth remembering that it takes a few weeks after vaccination before you are protected. For the Covid vaccines currently available in the UK, two doses, spaced weeks apart, are recommended to give the best protection.
However if you have already formed a support bubble with your father, you can have close physical contact with him.
Is it true that the vaccine can affect fertility? From Patricia, Weston-Super-MareMichelle Roberts Health online editor
Experts say there is no evidence that the vaccine affects fertility.
Those who intend to try to become pregnant do not need to avoid pregnancy after vaccination.
Will the vaccine last for the rest of your life, or will you have to have a vaccine every 12 months, like the flu jab? From Robert Parker, WarwickshireMichelle Roberts Health online editor
It’s not clear yet how long immunity might last after vaccination.
It is possible that people will need to be vaccinated annually or every few years to have protection.
Can I have the vaccine safely if I am allergic to penicillin? From James, BristolMichelle Roberts Health online editor
Yes. Allergy to penicillin is not listed as a clinical reason to avoid having either the Pfizer-BioNTech or the AstraZeneca-Oxford Covid-19 vaccine.
However, when you are invited for your Covid vaccine, you should discuss your allergies with healthcare staff to make sure there is no other reason to avoid it.
Vulnerable 65-70-year-olds have not been included in the first round of vaccinations. Will we definitely get the jab after the first group? From Ian Cross, WatfordMichelle Roberts Health online editor
Vaccines are being given to the most vulnerable first, as set out in a list of nine high-priority groups, covering around 30 million people in the UK.
People living in care homes, their carers and other frontline NHS staff are at the front of the queue.
People who are 70 or older, as well as clinically extremely vulnerable individuals (of all ages) will be immunised soon after, and as quickly as possible.
Will vaccination teams have regular coronavirus testing, so they don't infect the people they are protecting? From Ivan Young, Romsey, HantsMichelle Roberts Health online editor
The people giving the vaccines will be wearing appropriate personal protective equipment (PPE) to help prevent the spread of virus.
Some will also have already been vaccinated themselves, due to their occupation as healthcare providers.
Can I travel back home for my vaccination? I am living in a different county with my support bubble, but registered with my GP elsewhere. From Ida, Southend-on-Sea, Essex
Yes, you will be able to do that.
The whole of England, and most areas of the UK are currently under lockdown and people should stay at home.
However, you are permitted to travel to attend a medical appointment.
I’m currently in Gran Canaria Spain and planning to return to home (London) around 26th February. Do I need a PCR test? From M Rad, London
You will need to show evidence of a recent negative coronavirus test before you depart, if the new rules are still in force, but Transport Secretary Grant Shapps has indicated that several different types of test will be accepted.
From next week, passengers to the UK will need to prove at the start of their journey that they had a negative test for coronavirus less than 72 hours beforehand.
PCR tests are seen as the “gold standard” because of their high level of accuracy, but the results must be analysed in a lab, meaning they can take a day or more to come back.
The government has suggested rapid lateral flow tests will also be acceptable. These are quicker and often easier to obtain than a PCR test, usually offering results within half an hour.
Most UK arrivals – including those from Spain - must also quarantine on arrival for 10 days. You may be able to shorten your self-isolation time if you pay for a test after five days, and it comes back negative.
I am in Norway right now. My flight back to Aberdeen is on 12 January. I’m a permanent resident and my husband is Norwegian. What are the arrival requirements? From Dahliah Aziz, Aberdeen
From next week (exact date to be confirmed) new rules are being introduced for travellers arriving in the UK.
Before you board your flight from Norway, you will need to show a negative result from a recent coronavirus test. This includes UK citizens.
In Scotland, this measure will be introduced “as soon as practically possible”.
Anyone who tests positive for coronavirus will not be allowed to travel. Border Force will be carrying out spot checks on UK arrivals and those who do not fully comply with the roles face a £500 fine.
Some people will be exempt from the testing requirement, including under-11s, hauliers, and people arriving from the common travel area or countries which do not have the infrastructure to conduct tests – this is unlikely to include Norway.
Currently, people arriving in Scotland from Norway do not have to self-isolate. But Scotland and the rest of the UK is under a national lockdown, meaning that you should only make essential journeys after you arrive.
Why can’t the government decide to keep all pupils and students back a year so that no-one misses out on their education? From Anne Ellioy, Iver
Making children repeat a year at school is something rarely tried in the UK, even though it is fairly common in the US and some other countries.
Commenting in June, the Department for Education said it was down to individual headteachers to decide how to educate pupils. “This may, on occasion, include deciding that a child should be educated in a year group other than the one indicated by their age." It added: "Such decisions should be based on sound educational reasons and in consultation with parents.”
However, it’s not clear whether the strategy works. Analysis by researchers at Durham University found that pupils who were held back a year were likely to make four months less progress than if they moved up a year with everyone else.
What’s more, the cost of keeping a pupil back a year is expensive - an estimated £6000, far more than it would cost, for instance, to provide intensive tuition for struggling pupils.
My daughter wants to return to university, the course is online until February but her halls are paid for. Is she allowed back? From Jennifer Carter, Bath
It depends where in the UK her university is. In England, there is nothing explicitly stopping your daughter from going back to her halls, provided she has not been tested positive for coronavirus or is self-isolating. She also should not travel if she is displaying coronavirus symptoms.
Unless they are doing certain practical courses such as medicine or dentistry, most university students have been told to “remain where they are wherever possible” until at least mid-February and start their term online.
Students who go back to their university accommodation should either be tested twice upon their return, or self-isolate for 10 days, the government says.
The higher education guidance for England says there is no ban on moving house “where necessary” including forming new households and moving into shared houses or student accommodation, but it warns that moving households comes with a risk of higher transmission.
The Scottish government says that plans for students’ return should be developed in consultation with staff and students, and that arrivals should be staggered.
Students are allowed to travel into Wales from anywhere in the UK if it is to resume their studies. However, the government in Wales says students should not go back until they are told to by their university, when in-person learning will resume.
Can I go out for a walk with friends? From David Girling, Portishead
In England, Scotland and Northern Ireland you can walk with one friend – but not with a group.
Exercise is allowed with one person who is not in your household or support bubble, in a public outdoor place (for example, a park, a beach or in the countryside).
You can only exercise with one person at a time, and you should not exercise more than once per day. What’s more, you should not travel outside your local area.
In Wales, you are not allowed to exercise with anyone outside your household or support bubble.
Are support bubbles still allowed for single parents? It was not covered in the prime minister’s announcement. From Liz, Sheffield
Support bubbles were not mentioned in the prime minister's lockdown announcement but the rules have not changed.
You can form a support bubble with another household of any size if you are a a single adult living with one or more children who were still under 18 on 12 June 2020.
As a parent, you can also form a support bubble if your household includes a child who was still under the age of one on 2 December 2020, or a child with a disability who requires continuous care and is under the age of five.
Other reasons for a support bubble include living by yourself (even if carers visit you to provide support), or if you are the only adult in your household who does not need continuous care as a result of a disability.
You should not form a support bubble with a household that is part of another support bubble.
My elderly mum is my support bubble but she does not live locally (about a 90-minute drive away). Am I still allowed to go to see her? From Tina Howson, Leicester
There is nothing to stop you continuing your support bubble with your mother. Although the central message of the new lockdown is that everybody should stay at home where possible, the government's guidance says that you are permitted to leave your home and travel to visit your support bubble (and to stay overnight with them).
However, it's important that you follow guidelines when you leave home, which include social distancing, and not mixing with anyone other than your mother.
When driving to see her, you should also not share your car with anyone not in your household.
I am a nurse and my husband is recovering from blood cancer. Going to work means taking chances on his life. Can I be furloughed? From Lisha, Fareham
If your employer is eligible, you can ask them if you can be furloughed through the government's Coronavirus Job Retention Scheme.
While on furlough you would receive 80% of your normal pay up to a maximum of £2,500 a month.
The government has said that workers who need to look after their dependants are eligible for the scheme.
If you work for the NHS, where most employees are not eligible for the furlough scheme, you should speak to your employer. NHS employers have been advised to be as supportive and flexible as possible towards staff with caring committments.
I am 77 years old - do I have to stay in? From Maureen Watkins, Sheffield
The short answer is that we all have to stay at home, and only leave for a limited number of reasons, such as shopping, or work which cannot be carried out from home.
If you are also classed as clinically extremely vulnerable, you should be shielding, and only go out for medical appointments, exercise or if it is essential.
The government has drawn up a list of conditions which would make a person extremely vulnerable. Your GP may also add you to the Shielded Patients List if they think you are at greater risk of serious illness.
However, if you are in good health, your age is not itself a reason for you to shield.
Can you explain how the new variant of the Covid virus is more transmissible? What does this mean exactly? From Kevin WaiteMichelle Roberts Health online editor
The new variant is rapidly replacing other versions of the virus and passes more quickly from person to person.
Experts are studying the virus to understand what the changes might mean.
It is possible that the mutations make it easier for the virus to enter cells.
It might be that people who are infected with the new variant have more of the virus in their nose and throat and can spread it more easily when they cough and sneeze.
Why is this virus spreading so quickly if we are washing our hands endlessly? From Christine BymanMichelle Roberts Health online editor
This new variant does appear to be spreading more easily and becoming the dominant type of coronavirus in some parts of the UK.
But human behaviour is extremely important too. Following social distancing rules can help stop the spread. The new variant can still be destroyed with soap and water.
How do staff know that the vaccine they are giving you has not expired because of incorrect storage? From Keith, LoughboroughPhilippa Roxby Health reporter
Every vial, which contains several vaccine doses, is stored frozen and has to be thawed and then diluted before people are vaccinated.
Healthcare staff will be given detailed information on exactly how long the vials can be stored in a fridge (five days) and when they should be discarded after being taken out.
Prof Jonathan Van Tam says these considerations make this “delicate” vaccine more complicated to get to people in care homes and to the elderly in their own homes.
But this won’t be as much of an issue in hospitals where vaccine doses can be stored in bulk and used quickly on staff and patients.
Is it safe for pregnant women and their babies to take the vaccine? From Abbie Rankin, DumfriesPhilippa Roxby Health reporter
At present, women are not advised to have a Covid vaccine during pregnancy, or if they are planning to get pregnant in the next three months.
There are no safety concerns from any of the data but, as in most trials, the vaccine has not yet been tested on pregnant women.
As a result, the official advice is that women should postpone being vaccinated until they have given birth.
NHS guidance says that if a woman finds out she is pregnant after having the first dose, she should not have the second dose until after the pregnancy has ended.
The vaccine distribution will be largely prioritised by age, so the majority of pregnant women would be low down on the list to receive it in any case.
Even pregnant women who are at higher risk of coronavirus – with underlying heart conditions, for example – should wait until after their pregnancy and then have the jab as soon as possible afterwards.
How can we be sure the vaccine is safe with such a short testing period? From Maddie MRachel Schraer Health reporter
Although it’s been done quickly, this vaccine trial hasn’t skipped any of the usual steps.
The only difference is that some of the stages overlapped so, for example, phase three of the trial – when tens of thousands of people are given the vaccine – started while phase two, involving a few hundred people, was still going on.
Side effects usually show up quite quickly after vaccination and longer-term effects are extremely rare – much, much rarer than long-term side effects of the virus.
Usually vaccine trials are slowed down by long periods of waiting around, applying for permission, funding and resources.
It’s those elements that were sped up, because of the huge global interest in doing so.
When the rollout of the vaccine begins with the priority 1 group, will those in that group who have had Covid already, be vaccinated? From Neil, CroydonRachel Schraer Health reporter
People will be vaccinated whether or not they’ve had Covid.
We don’t yet know how long natural immunity lasts, and vaccination can offer better protection than immunity from the disease itself.
Is the vaccine compulsory? From Kim, North YorkshirePhilippa Roxby Health correspondent
No, people in the UK are not being told they must have the vaccine.
However, those in the most at-risk groups (over-70s and care home residents), and people who work in care homes and for the NHS will be expected to have it - to protect themselves and the people they care for.
Making a vaccine mandatory is not usually recommended because it can lower confidence in the jab.
How long will immunity last once vaccinated? From Seth Harris, NorfolkPhilippa Roxby Health correspondent
Scientists don’t know the exact answer to that at the moment.
The volunteers in the vaccine trials who were given the jab will be followed up for many months to come to check how long they are protected for.
Natural immunity to the virus, once someone has been infected, appears to last at least six months so it’s likely a vaccine will offer this length of protection and hopefully a lot more.
What must people do after receiving a coronavirus vaccine? Carry on life as normal, wear a mask, adhere to distancing rules? From Mary MullensMichelle Roberts Health online editor
The vaccine significantly reduces the risk of getting seriously ill with coronavirus. But it is unclear whether it stops people from catching the virus or passing it on to others.
So it is really important that people continue with social distancing, wearing face coverings and washing their hands, even if they have been immunised.
Is the Oxford vaccine suitable for people whose immune systems are not strong, such as transplant recipients? From Carol Olley, NewcastleMichelle Roberts Health online editor
If your immune system is suppressed and not working as well as it might, some "live" vaccines are not recommended. This is because the weakened virus they are made from could cause problems.
The Oxford vaccine is not a "live" vaccine. Scientists are testing which patients could benefit from it and whether this might include people with certain health conditions, or who are taking particular medication or undergoing treatment for something else, such as cancer or HIV.
There are lots of different Covid vaccines in development and some may be more suitable for different groups than others.
Is the Oxford AstraZeneca vaccine any safer or more traditional than Pfizer and Moderna’s vaccines? From Tom Haslam, LeicesterMichelle Roberts Health online editor
These three different Covid vaccines all appear to be safe and effective in trials. It will be up to regulators to check the data and decide whether to approve the jabs for widespread use.
The Oxford vaccine is based on a more traditional method for making vaccines than the Pfizer and Moderna ones. It uses a modified, harmless cold virus to carry the genetic information on Covid into the body to get the immune system to mount a response. The Oxford team has already used this technology to make vaccines for other diseases, including flu. The Pfizer and Moderna vaccines use a brand new method for making a vaccine.
They contain a small amount of genetic code, made in the lab, to match the spike protein on the surface of the pandemic virus. This does not alter the genetics of human cells though, but triggers the immune system to make antibodies that can fight Covid.
My husband is allergic to eggs and cannot have a flu jab because they use egg to culture the vaccine. Is it the same with COVID-19 vaccines? From Yvone, AlburyMichelle Roberts Health online editor
Neither the Pfizer jab nor the Covid vaccines that could soon be approved for use - Moderna or Oxford/Astrazeneca – are made using eggs so there should be no issue for people with egg allergies.
Is there any point taking the Oxford vaccine as it is not effective enough? From A FrostMichelle Roberts Health online editor
No vaccine is 100% effective for everyone. And 70% is still very good, particularly for a disease as serious as Covid-19.
US regulators had said they would accept 50% protection as worth pursuing for Covid. Flu jabs are between 40% and 60% effective.
Will I be able to choose which vaccine I receive? From Sarah, OadbyMichelle Roberts Health online editor
Only one vaccine has been approved so far.
If more than one gets the green light from regulators, then the priority will be getting doses out to the people who need it the most, as quickly as possible.
These steps will determine which vaccines are available first and can be offered to patients. It is unlikely that people will be able to pick and choose.
Does the Moderna vaccine have storage and distribution constraints similar to the Pfizer vaccine? From Colin HayesMichelle Roberts Health online editor
Both vaccines need to be stored at below freezing temperatures when they are transported from the factory out to clinics.
The Pfizer jab needs to be kept at around -70C, which is somewhat challenging, while the Moderna one can be kept in a normal freezer temperature of -20C.
Both can be thawed and kept in a fridge once they arrive at the clinic, but the Pfizer one then has a short shelf life of five days compared to four weeks for the Moderna vaccine.
If the vaccine is successful and vaccination begins, how will I know if the people around me in a public place have been vaccinated? From David Rowe, CrawleyMichelle Roberts Health online editor
Initially, only a small proportion of society will be offered a vaccine. The first stocks reaching the UK will be offered to those who need protecting from coronavirus the most in terms of disease severity – the elderly living in care homes and the health staff who work there.
Medical notes will say if an individual has been given the vaccine, but these are private records. There is no suggestion yet that people will need to carry proof of immunisation.
What is the difference between a recovery with a small chance of reinfection, and a vaccine that is only 90% effective? From Clark, KidderminsterMichelle Roberts Health online editor
People can get immunity to coronavirus either naturally – when they have been infected – or via a vaccine.
A vaccine that is 90% effective means that most people (nine in every 10) who are immunised will get some protection against the disease.
The big question is how long does this protection last? Scientists do not know the answer, either for natural immunity or vaccine-induced immunity.
I have been waiting for two months for a skin cancer biopsy. Will the Covid 19 vaccination programme mean I wait longer? From Bill Singleton, BristolMichelle Roberts Health online editor
The NHS has been planning how best to roll out the vaccine. It will be a large-scale immunisation programme, requiring lots of trained staff to administer the jabs.
Pharmacists, nurses, doctors and other healthcare professionals will be able to vaccinate people in a range of settings – including care homes, hospitals and GP clinics as well as pop-up centres, such as sports stadiums and conference buildings.
It could mean some delays to some non-Covid NHS services, but urgent and essential care will be prioritised. The aim is to keep usual services running whenever possible. You could contact your GP to discuss any concerns you have.
Whilst the vaccine will not be mandatory, is it possible that establishments could make proof of vaccination a condition of entry? From Will Ho, LondonMichelle Roberts Health online editor
Some countries require proof of vaccination for other diseases - for example, for polio. It will be up to individual countries to decide their own vaccination policy for Covid and whether an immunisation certificate is necessary in the future for travellers.
There was also a suggestion when Prime Minister Boris Johnson talked about his "Moonshot" plan for mass rapid testing, that a negative on-the-day result would allow people to go to the theatre or a football match.
Given that the Pfizer/BioNtech vaccine needs to be stored in ultra-low temperature, would there be any major logistical challenges in that respect? From JackMichelle Roberts Health online editor
The ingredients in the Pfizer/BioNtech vaccine are not very stable and need to be kept at below -70C until before use.
That means it must be transported carefully. But it must be thawed before it is given to a patient and Pfizer says the jab remains viable for up to five days kept in a normal fridge before it is administered.
Will the new vaccine protect against mink-mutated Covid? From Daemon GriffithsMichelle Roberts Health online editor
Experts have recently discovered mutations in the genetic code of coronavirus that appear to have happened when mink caught the disease from humans and then passed it back to people.
Scientists are studying these alterations to see if they have significantly changed the behaviour and threat of the virus to mankind. So far, there is no evidence that the mutations pose an increased danger to people or that they will undermine the effectiveness of any Covid-19 vaccines.
All viruses mutate to some extent over time. Some changes can make a virus less lethal or contagious. Flu – a different virus to Covid – changes frequently, which is why the annual flu vaccine changes too, to keep pace.
Currently the NHS tracing app requires IOS13.5 or above to install, so it is not compatible with older phones. Is there a workaround? From Taraka
If you can't download the new NHS Covid-19 tracing app, it is probably because your phone runs on an older operating system. The app will only work on a certain number of newer models.
This is because it uses technology only recently developed by Apple and Google, which will not work on earlier operating systems.
Your phone must have the IOS 13.5 operating system installed (released in May 2020), or Android 6.0 (released in 2015), as well as Bluetooth 4.0 or higher.
This excludes the iPhone 6 or any earlier models, as well as old versions of Apple’s handsets (and some newer Huawei phones).
If your smartphone is not compatible, the NHS Test and Trace Service is still the first port of call for any contact tracing issues.
My wife and I currently live apart until I retire. I live in Cumbria, she lives in Fort William. Which tracing app should I use? From Nick Jowett, Burgh-on-Sands, Cumbria
Apple and Google's framework will not allow two apps to contact trace simultaneously.
So when you cross the border from England to Scotland, you need to open the Scottish app and turn on contact tracing within it. This will bring up a prompt asking: "Switch app for exposure notifications?" When you do this, it will turn off the app you were using beforehand.
I have a bar and restaurant and I have just watched BBC news report on the new NHS app and QR code. Where do we obtain the QR code? From Steve Capewell, St Columb, Cornwall
You can get your own unique QR code at this government website. All you need to enter is your email and your restaurant's address.
Every business, place of worship, event and community organisation with a public space should create a unique QR code they can display for visitors to scan.
You can then print off a QR code poster. It’s a good idea to put the QR poster near the entrance, so that visitors can log their location by scanning the poster with the track and trace app when they arrive.
If you run more than one venue, you will need to create a separate QR code for each location.
I have hearing aids which are connected to my smartphone via Bluetooth, will this affect the operation of the app? From Richard Smith, Milton Keynes
The government says that the app “has been designed to work in the phone’s background, working alongside other Bluetooth features and devices”, so your hearing aids should be unaffected.
If you do find some interference, there is an online form to report this to them.
There have been no reports of interference between the app and medical devices in trials, but the government says it is sensible to be cautious when you rely on a medical device – in particular, it has included advice for people who use pacemakers.
What is the coronavirus? from Caitlin in Leeds Most askedBBC News Health team
Coronavirus is an infectious disease discovered in China in December 2019. Its more precise name is Covid-19.
There are actually hundreds of coronaviruses - most of which circulate among animals, including pigs, camels, bats and cats. But there are a few - such as Covid-19 - that infect humans.
Some coronaviruses cause mild to moderate illnesses, such as the common cold. Covid-19 is among those that can lead to more serious illnesses such as pneumonia.
Most infected people will have only mild symptoms - perhaps a fever, aching limbs a cough, and loss of taste or smell - and will recover without special treatment.
But some older people, and those with underlying medical problems such as heart disease, diabetes, or cancer are at greater risk of becoming seriously unwell.
The NHS has more about symptoms.
Once you've had coronavirus will you then be immune? from Denise Mitchell in Bicester Most askedBBC News Health team
When people recover from an infection, their body is left with some memory of how to fight it should they encounter it again. This immunity is not always long-lasting or totally efficient, however, and can decrease over time.
It is unclear, though, if people who have recovered from coronavirus will be able to get it again.
Hong Kong scientists have reported the first case of a man who was reinfected with coronavirus, although the World Health Organization has warned against jumping to conclusions on the basis of one case.
University of Oxford’s Prof Sarah Gilbert, who is working on creating a vaccine for Covid-19, says that it “probably is likely” that an infected person will be able to be reinfected in the future.
What is the incubation period for the coronavirus? from Gillian GibsMichelle Roberts Health online editor
Scientists have said that the “incubation period” - the time between catching the virus and starting to show symptoms - is five days on average. However, some people can have symptoms earlier or much later than this.
The World Health Organization advises that the incubation period can last up to 14 days. But some researchers say it may be up to 24 days.
Knowing and understanding the incubation period is very important. It allows doctors and health authorities to introduce more effective ways to control the spread of the virus.
Is coronavirus more infectious than flu? from Merry Fitzpatrick in SydneyMichelle Roberts Health online editor
Both viruses are highly contagious.
On average, it's thought people with the coronavirus infect two to three other people, while those with flu pass it on to about one other person.
There are simple steps you can take to stop the spread of flu and coronavirus:
- Wash your hands often with soap and water
If you have returned from holiday abroad and have to self-isolate in quarantine, you will not automatically qualify for Statutory Sick Pay (SSP), so it's possible you might have to make arrangements with your employer if you cannot work from home.
- Catch coughs and sneezes in a tissue and then put it in the bin
How long can you be ill? from Nita in MaidstoneBBC News Health team
For four out of five people Covid-19 will be a mild disease, a bit like flu.
Symptoms include [fever, a dry cough or loss of smell and taste(https://www.bbc.co.uk/news/health-51048366)
If the virus gets well established in the lungs it can cause breathing difficulties and pneumonia. About one in seven people may need hospital treatment.
Recovery time will depend on how sick you became in the first place. Some people shrug off the illness quickly, but for others the path to full health can take months, and leave lasting problems.
Asymptomatic people are regarded as "silent spreaders" - what proportion of the population are they estimated to be and how do you find them? From Val Holland in Worcester
This is the subject of ongoing research, but little is still known about how many people are carrying the virus without knowing it.
Different studies currently suggest a huge range of possibilities for how many "silent spreaders" there are - ranging from 5% to 80% of cases. That was the conclusion of an analysis by Prof Carl Heneghan of the University of Oxford and colleagues who looked at 21 research projects.
The upshot, they said, was that "there is not a single reliable study to determine the number of asymptomatics". And they said that if the screening for Covid-19 is only carried out on people with symptoms - which has been the main focus of UK testing policy - then cases will be missed, "perhaps a lot of cases".
Some scientists believe that asymptomatic cases may be the main force driving the pandemic, and there have been calls for increased testing to establish how many "silent carriers" there may be.
Why are diabetics not included in the clinically extremely vulnerable patients, and will the list be refreshed? from Derek Roberts in Hornchurch, EssexMichelle Roberts Health online editor
Diabetics are not included in the list of people at highest risk. However, some may be advised to take extra precautions if they suffer from a combination of factors, such as heart disease or obesity, as well as diabetes - which put them at much higher risk of complications.
A third of virus deaths in England from 1 March to 11 May were linked to diabetes, but research suggests the threat for those under 40 with type 1 (insulin-dependent) or type 2 diabetes is still very low.
Age remains the strongest risk factor for becoming severely or fatally ill with coronavirus, say experts.
Diabetes UK advises anyone with diabetes to try their best to manage their condition carefully, keeping their blood sugar in range as much as possible, as well as following social distancing measures.
How dangerous is coronavirus for people with asthma? from Lesley-Anne in FalkirkMichelle Roberts Health online editor
Asthma UK's advice is to keep taking your daily preventer inhaler (usually brown) as prescribed. This will help cut the risk of an asthma attack being triggered by any respiratory virus, including coronavirus.
Carry your blue reliever inhaler with you every day, in case you feel your asthma symptoms flaring up. If your asthma is getting worse and there is a risk you might have coronavirus, contact the online NHS 111 coronavirus service.
Are otherwise healthy disabled people more at risk from coronavirus? from Abigail Ireland in StockportBBC News Health team
Coronavirus can be more severe in older people and those with pre-existing conditions such as heart and lung illnesses, or diabetes.
There is no evidence that disabled people who are otherwise healthy - and who don't, for instance, have respiratory problems - are at greater risk from coronavirus.
Will people who've have had pneumonia experience milder coronavirus symptoms? from Marje in MontrealBBC News Health team
Covid-19 can, in a small number of cases, lead to pneumonia, most notably in people with pre-existing lung conditions.
But as this is a new virus, no-one will have any immunity to it, whether they have previously had pneumonia, or any other form of coronavirus such as Sars.
With key workers wearing some sort of mask, how are deaf people who lip-read supposed to understand what is being said? From Margaret Roll in Clevedon
Wearing masks presents major challenges for some deaf people who rely on lip-reading to communicate, but who also need to stay safe from catching the virus, especially if in a hospital setting.
The charity Action on Hearing Loss says there are some clinically approved see-through covered face masks that help enable lip-reading. However, they do not provide enough protection against aerosols spread by coronavirus, and wouldn’t be right for health and social care workers to use during this pandemic.
Many of the experimental coronavirus jabs currently being tested contain the genetic instructions for the surface spike protein that coronavirus uses to attach to and infect human cells. Reassuringly, scientists have not seen any substantial mutations to this part of the virus yet that would render these vaccines useless.
What should I do if someone I live with is self-isolating? from Graham Wright in LondonBBC News Health team
If you’re living with someone who’s self-isolating, you should keep all contact to a minimum and, if possible, not be in the same room together.
The person self-isolating should stay in a well-ventilated room with a window that can be opened, and keep away from other people in the house.
If you live with someone who has symptoms, you'll also need to self-isolate for 14 days from the day their symptoms started.
If you get symptoms, self-isolate for 14 days from when your symptoms start, even if it means you're self-isolating for longer than 10 days. If you do not get symptoms, you can stop self-isolating after 10 days.
If you or your housemates develop symptoms after 00:01 GMT on Monday 14 December, you will only have to self-isolate for 10 days.
Should people stop having sex? from Martha Menschel in Las Vegas
If you live with your partner, they count as being part of your household. If neither of you is showing coronavirus symptoms and you are already in close contact, having sex won't increase the likelihood of you catching the virus from one another. If one person does have symptoms, they should be self-isolating in a separate room.
Using contraception such as condoms won't alter your risk of catching the virus, as having sex will bring you into close physical contact anyway.
"If you are going to touch each other's genitals it's likely that you will potentially be kissing at the same time - and we know the virus is passed through saliva," Dr Alex George told the BBC's Newsbeat.
"Essentially, any possibility of transfer of coronavirus - from your mouth to your hands, to genitals, to someone else's nose or mouth - increases the risk of passing on coronavirus."
I am five months pregnant and want to understand the risk to the baby if I get infected? from a BBC website readerJames Gallagher Health correspondent
Pregnant women are being advised by the UK government to stay at home and keep contact with others to a minimum. However, they should attend antenatal clinics as normal.
There is no evidence to suggest that pregnant women are more likely to get coronavirus. But, for a small number of women, being pregnant may change the way their body deals with a severe viral infection.
The government’s chief medical adviser says this is a precautionary measure until scientists find out more about the virus and that "infections and pregnancy are not a good combination in general”.
I am breastfeeding my five-month-old baby - what should I do if I get coronavirus? from Maeve McGoldrickJames Gallagher Health correspondent
Mothers pass on protection from infection to their babies through their breast milk.
If your body is producing antibodies to fight the infection, these would be passed on through breastfeeding.
Breastfeeding mums should follow the same advice as anyone else over reducing risk - cover your mouth when you sneeze and cough, throw away used tissues straight away and wash hands frequently, while trying to avoid touching your eyes, nose or mouth with unwashed hands.
Is it possible to catch coronavirus from a pet dog or cat? from Javed
This is highly unlikely to happen, according to scientists and vets.
While there are rare cases where an animal has caught the virus from a human, there is no evidence that humans can catch the virus from animals.
It is possible that a pet's fur could become contaminated if an infected person has previously touched or stroked the animal.
But even without the threat of coronavirus, you should always wash your hands with soap and water after handling an animal or its lead, and avoid touching your nose and mouth.
I'm self-employed. Can I claim benefits if I can't work due to the virus? from Mark Gribby in NottinghamSimon Gompertz Personal finance correspondent
Self-employed people who have symptoms or have been told to self-isolate may apply for two benefits - universal credit or employment and support allowance.
Normally, you would be eligible after four days of being ill. However, the government has responded to the spread of coronavirus by saying that companies will temporarily pay SSP from the first day off.
But charities are worried that there is still a five-week delay before universal credit is paid.
Who is eligible for universal credit? from Mario in LondonMoneybox team BBC Radio 4
Anyone aged 18 or above can apply for universal credit if they live in the UK and are on a low income or out of work.
Students in full-time education aren’t usually eligible for universal credit, but they can make a claim if they do not have any parental support, are responsible for a child or are in a couple with a partner who is eligible for universal credit.
People aged 16 or 17 can also apply for universal credit if they do not have any parental support, are responsible for a child, caring for a disabled person or cannot work.
You can use the government's benefits calculator to find out how much you may be entitled to.
If you have to self-isolate will you only get statutory sick pay, or will your employer pay your salary? from Laura White in Herefordshire
The government advises that people who are self-isolating should work from home wherever possible and be paid as normal.
If they can’t work from home, employers must ensure any self-isolating employee gets sick pay or is allowed to use paid leave days if they prefer.
Employees in self-isolation are entitled to Statutory Sick Pay for every day they are in isolation, worth £95.85 per week, as long as they qualify.
However, employers can choose to pay staff their full wages during this period if they wish.
What are my chances of getting a job in lockdown/when lockdown is over? from Jess in EssexMoneybox team BBC Radio 4
Research conducted by the Resolution Foundation has found that the coronavirus pandemic could increase youth unemployment by 600,000 this year.
If you’re worried about finding a job you can head to the National Careers Service for advice on how to find job vacancies.
You can also search online for virtual job fairs. This could help you explore different job opportunities and connect with potential employers directly from home.
Experts recommend using lockdown to refresh your CV and also look for any online training opportunities which might put you in a better position when you eventually apply for a job.
Can I travel to Ireland and then onto another country, then back to the UK via Ireland to avoid the quarantine? from Chris McCann in Sandhurst
The short answer to this is no.
It's true that you don’t have to go into quarantine if you’re returning to the UK from what’s known as the Common Travel Area (CTA) - Ireland, Isle of Man and the Channel Islands.
When the government first announced its plans, there was some speculation that to avoid quarantine, travellers from other countries would be able to fly into an airport in the CTA, and then on to the UK and so avoid having to self-isolate.
However, this loophole (termed by some the "Dublin dodge") has now been closed by the government. Travellers will only be exempt from quarantine if they have been in the CTA for 14 days or more.
You will have to show proof of when you entered the CTA, and how long you have spent there - such as a boarding pass or itinerary - when you enter the UK.
Do key workers have to quarantine? From Mateusz in London
Key workers will not necessarily be exempt.
The government has published a detailed list of who will not need to follow the quarantine rules. Among others, it includes road haulage and freight workers, medical and care professionals providing essential health care, some seasonal agricultural workers, Eurostar and Eurotunnel employees, pilots and aircrew and people working to maintain key infrastructure such as the railways.
It also depends where you are going in the UK - some employees will be exempt from quarantine in England and Wales, but not Scotland.
The government guidance details what you’ll need to show when you enter the UK to prove you are exempt. This differs between categories but typically includes proof of your name and address, the name of your employer and what work you’ll be doing.
Will my flatmates have to quarantine as well because of me? From Matteo in London
Unless your flatmates were travelling with you, they do not need to self-isolate or quarantine with you.
However, you must avoid contact with them and minimise the time you spend in shared spaces like kitchens, bathrooms and sitting areas.
You should stay in a well-ventilated room with a window to the outside that can be opened, separate from your flatmates, and if you can, you should use a separate bathroom from them. If you do need to share these facilities, regular cleaning will be required after each person has used them.
Make sure you use separate towels from the other people in your house, both for bathing and showering, and for washing your hands.
If I have to quarantine after a holiday and can’t work from home will I get paid? From Emma in Portishead, Bristol
If you have returned from holiday abroad and have to self-isolate in quarantine, you will not automatically qualify for Statutory Sick Pay (SSP), so it's possible you might have to take the extra time off as annual leave, or else as unpaid leave.
The Department of Work and Pensions says that anyone planning to travel should do so in the knowledge that they will be required to self-isolate on their return.
It adds that employers and staff should discuss and agree any arrangements in advance, and urges employers to take socially responsible decisions.
Meanwhile, the Foreign & Commonwealth Office is still advising UK nationals against taking all but essential international travel.
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