Several countries have suspended use of the Oxford-AstraZeneca vaccine following reports of blood clots in a handful of people who have had the jab.
Denmark, Norway, Bulgaria, Iceland, Ireland, Germany and the Netherlands have all temporarily suspended their use of the AstraZeneca jab.
The countries decided to do so over concerns of possible side effects.
Last week, the World Health Organisation (WHO), the European Medicines Agency (EMA) and the UK's Medicines and Healthcare products Regulatory Agency (MHRA) said there was no evidence of a link between the jab and an increased risk of blood clots.
More than 11 million Brits have had the Oxford-AstraZeneca jab with some concerned that they could face health issues.
So how big is the risk, and is there any reason to be worried?
Have you had the vaccine? Tell us about your experience in the comments below.
Why are people worried?
Because several European medical bodies have reported health issues in a small number of people who have had the vaccine.
In Austria a man died 10 days after being vaccinated having been admitted to hospital with pulmonary embolism, the European Medicines Agency confirmed.
A review from Norway's medicines agency showed four new cases of "serious blood clotting in adults", while another death involving a blood clot was reported in Denmark.
In Italy a 50-year-old man is thought to have died of deep vein thrombosis having had the jab.
Are the health issues directly linked to the Oxford-AstraZeneca jab?
The overwhelming verdict from health experts is no, they are not linked to the jab but may instead be a pure, statistically likely coincidence.
Blood clots are fairly common, which means that given the large number of people who have been vaccinated, it would be weirder if none of them fell ill with the condition.
Of almost five million people given the vaccine across Europe, there have been just 30 reports of blood clots, the EMA has said.
Last week the World Health Organisation looked to reassure people and governments that the vaccine was safe to use and a key part of the pandemic response.
A spokesperson for the organisation said "no causal relationship had been established between the shot and the health problems reported".
What have UK scientists said?
The head of the Oxford University vaccine group Professor Andrew Pollard said that while "safety is clearly absolutely paramount", about 3,000 cases of blood clots occur every month in the UK from other causes.
"So, when you then put a vaccination campaign on top of that, clearly those blood clots still happen and you've got to then try and separate out whether, when they occur, they are at all related to the vaccine or not," he told BBC Radio 4's Today programme.
Prof Pollard said that more than 11 million doses have now been given in the UK, and the MHRA has said "very clearly that they're not seeing any increase in the number of cases of blood clots" over what they would see normally.
The Medicines and Healthcare products Regulatory Agency said evidence "does not suggest" the jab causes clots, which has led Northern Ireland's First Minister Arlene Foster to urge people to take the vaccine.
"I am looking forward to taking it, either this week or next week, depending on when I am able to get my vaccine booked for, but it is very important that people continue to take the vaccine," she sad this morning.
"We have made huge progress in the UK in relation to the vaccine, so it is important that people continue to do that so we can leave lockdown in the rearview mirror and we can move on with our lives."
So why have countries suspended use of the jab?
In short, because their health authorities want to make sure the health concerns aren't linked to the vaccine before more people get the jab.
The Republic of Ireland's deputy chief medical officer, Dr Ronan Glynn, recommended the vaccine stop being used for now while acknowledging that "it has not been concluded that there is any link" between the jab and the clotting cases reported in Norway.
"However, acting on the precautionary principal, and pending receipt of further information, the NIAC (National Immunisation Advisory Committee) has recommended the temporary deferral of the Covid-19 vaccine AstraZeneca vaccination programme in Ireland," he said.
What have AstraZeneca said about the suspensions?
A fresh statement from AstraZeneca also looks to reassure the public that the vaccine is safe.
"A careful review of all available safety data of more than 17 million people vaccinated in the European Union and UK with Covid-19 Vaccine AstraZeneca has shown no evidence of an increased risk of pulmonary embolism, deep vein thrombosis or thrombocytopenia, in any defined age group, gender, batch or in any particular country," a spokesperson for the company said.
Should I get the Oxford-AstraZeneca jab?
Yes, although you won't know which vaccine brand you're going to receive until you get to the appointment.
So far the data do not show an increased risk of pulmonary embolism, deep vein thrombosis or thrombocytopenia for those who have had it.
What they do show however, is that the millions of vaccinations done each week are bringing the number of cases and deaths down.
More than 23 million people have now received a first dose of the coronavirus vaccine in the UK, with Department of Health data showing a recent steady decrease in cases and deaths.
A number of other countries which have not had such extensive vaccine rollouts are starting to see their cases tick up.
Professor Pollard pointed to the "huge risks" from Covid-19 for those who are unvaccinated, adding that "if we have no vaccination and we come out of lockdown in this country, we will expect tens of thousands of more deaths to occur during this year".
He continued: "A number of countries around Europe are now seeing an increase in cases again.
"Italy and France and Germany and Poland - all have the start of a new surge in cases.
"It's absolutely critical that we don't have a problem of not vaccinating people and have the balance of a huge risk - a known risk of Covid - against what appears so far from the data that we've got from the regulators - no signal of a problem."
If you've already had your first jab but not your second, it's important to go back, as this increases your protection against the virus.
The Prime Minister's official spokesman said: "The Oxford/AstraZeneca vaccine remains both safe and effective, and we urge anybody asked to come forward to receive a vaccine to do so."
There was "no evidence" that blood clots are any more likely to occur following vaccination, the spokesman said.
Several countries have temporarily suspended the use of the jab over concerns about blood clots.
What should I do if I start suffering from health problems after getting the vaccine?
The data show that most people will not suffer any side effects after getting the Oxford-AstraZeneca jab.
For those who do, the common ones are usually mild, include a sore arm where you were vaccinated, a headache, feeling achy, feeling sick and being tired.
These tend to last only a day or two and are not a cause for concern, but the NHS says people can take paracetamol if they want to.
If the health problems persist or get worse, then seek medical advice as you would for any other ailment.
Professor Anthony Harnden, deputy chairman of the Joint Committee on Vaccination and Immunisation, said women were more likely to get them from the Oxford/AstraZeneca jab than were men.
"The Oxford/AstraZeneca vaccine - for the first dose - seems to give quite a lot of minor side effects like: a very sore arm; fever; malaise; headache and sometimes chills which may last for up to 48 hours afterwards," he said.
"They do seem to be more common in women and in younger women.
"With the Pfizer vaccine, which we are given at the moment, it seems to be the reverse - side-effects are more likely with the second vaccine.
"The message is once you've had your first Oxford/AstraZeneca vaccine - if you do get some side-effects which are unpleasant, take some paracetamol."
He said people should not be deterred from having a second dose.
