This week is was revealed that under 40s will be offered an alternative to the Oxford/AstraZeneca coronavirus vaccine.
The Joint Committee on Vaccination and Immunisation (JCVI) made the decision after confirming there is an 'extremely small risk' of people suffering rare blood clots after having the jab.
However, the risk of serious illness with coronavirus also drops for younger people who have had the vaccine.
Professor Wei Shen Lim, Covid-19 Chair for JCVI said that safety remains the number one priority, BirminghamLive reports.
Those who have had the Oxford/AstraZeneca vaccine are now being urged to 'look out' for these five symptoms that could spell trouble.
The five worrying signs have been circulated by expects - and they are as follows:
Dr June Raine, chief executive for the Medicines and Healthcare products Regulatory Agency, said: "Things to look out for as we continue to monitor this issue, anyone who has symptoms for days after vaccination, should seek prompt medical advice.
"A new onset of a severe or persistent headache, or blurred vision, shortness of breath, chest pain, legs swelling, persistent abdominal pain, or unusual skin bruising or pinpoint spots beyond the injection site."
The Medicines and Healthcare products Regulatory Agency (MHRA) is currently appraising the jab and the review is said to be at an advanced stage.
Experts have also assessed the risks from any third wave of Covid in the UK and concluded that that wave is likely to be smaller than previously anticipated, therefore the risks to younger people are lower.