A new study has found headaches and tenderness at the injection site to be the most common side effects following vaccination against coronavirus.
One in four people had wider effects such as nausea and fatigue, but these symptoms lasted just a day on average.
The lead scientist on the study, Prof Tim Spector of King's College London, said the findings should reassure people that vaccine side effects are "usually mild and short-lived".
The study, run by researchers from the ZOE Covid symptom study in conjunction with the National Institute for Health Research, analysed self-reported symptoms in 627,383 who inputted information into their symptom app in the eight days following vaccination.
It found that around 70 per cent of those receiving the Pfizer jab reported a reaction at the site of injection, including redness, swelling or tenderness.
Just under 60 per cent of those who received the AstraZeneca jab reported the same symptoms.
Around 34 per cent of those who received the AstraZeneca jab reported systemic - whole body - reactions to the jab such as chills or tiredness.
This was lower for those who received the Pfizer vaccine, at just 14 per cent after the first dose and 22 per cent after the second.
The most common systemic reaction was a headache.
Both types of side effect after both types of vaccine were found to occur “at frequencies lower” than those recorded in trials, according to the study, published in The Lancet Journal.
Overall, one in four (25 per cent) people had a whole body reaction to being vaccinated, while two-thirds (66 per cent) had a local reaction - i.e. a reaction at the site of injection.
Side-effects were found to vary depending on a person’s age and sex, with people under 55, those who had previously contracted Covid and women all more likely to experience side effects.
Dr Cristina Menni from King's College London, lead author of the paper, told the BBC the study supported vaccine safety and should "help allay safety concerns of people willing to get vaccinated".