MORE people are experiencing side-effects with the Oxford AstraZeneca vaccine than the Pfizer drug, according to new data.

Around three in ten people who had the Oxford vaccine reported temporary, systemic after-effects including tiredness, headache or chills, compared to one in ten who received the other vaccine.

However experts said clinical trials had shown that patients are more likely to experience symptoms after the second dose of the Pfizer drug while the reverse is likely with the Oxford vaccine.

Denmark, Norway and Iceland have suspended use of the Oxford/AstraZeneca vaccine in a “precautionary” move after a Danish woman died with blood clots following inoculation. However, the World Health Organisation said there was 'no indication' of a link.

The first real world data collected through the King's College London Zoe tracking app and involving 700,000 UK participants, found that women, younger people and those who have already had Covid-19 were more likely to experience side-effects from both vaccines.

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However, the research team said this did not mean people were more or less protected than someone who did not feel unwell.

The data shows that both vaccines reduced the risk of infection to a similar extent seen in larger clinical trial - with a 70% reduction in mild disease. 

Some of the most unusual side-effects reported through the app were sore ears, tinnitus and "smelling petrol all the time". The rate of side-effects was less than expected from any of the clinical trials.

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Nurses involved in the care of adults with congenital heart disease said there had been reports of some patients suffering irregular heart beats after vaccinations.

A panel of experts drawn together to comment on the findings, said it was reassuring that those with underlying health conditions were no more likely to suffer side-effects than healthier individuals.

The app asks participants to record the date of vaccinations and any side-effects and found that in some cases symptoms were actually Covid-19 infections.

Eli Barnes, a professor of experimental medicine at Oxford University, said: "The side effects that you get are related to your innate immune response, which is your immune system's first line of defence to either an infection or to a vaccine.

"That is quite a separate thing from the kind of T-cells and antibodies that protect you from subsequent infection later on, which takes much longer to evolve."

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Prof Barnes said that while both vaccines were considered safe for patients with weakened immune systems, it is not yet known how effective they are for patients in this group including those with cancer.

New real-world data published yesterday found cancer patients are much less protected against Covid-19 than other people after one dose of the Pfizer vaccine.

Three weeks after one dose, an antibody response was found in 39% of people with solid cancers, compared to 97% of people with no cancer.

Dr Sheeba Irshad, oncologist and senior study author from King's College London, said the findings were "really worrying" and cast doubt on whether cancer patients should face a 12-week wait for the second dose.

Up to 5000 patients are being recruited in three cities including Glasgow to investigate the efficacy of the vaccine in patients with compromised immunity.

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Prof Barnes said there were "interesting" reasons why more women were more likely to report vaccine side-effects.

She said: "The two genders have a different immune system to some extent. Women are generally better at coping with infectious diseases generally. 

"They are more able to counter things like influenza, they respond better to vaccines, there is less childhood mortality in little girls than boys - actually it starts as young as that.

"Man flu is actually a real thing. When a man has got influenza, he's actually got a higher viral load - he is more sick.

"So all those people who have been rude to their partners about man flu - they should feel really bad about that because he really will be feeling more unwell.

"And all of that is probably reflected potentially in the side effects we are seeing here.

"It's interesting. On the counter side of that women get more auto-immune diseases because sometimes they have a more over-active immune system and men don't have that."

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Some people who had experienced a more severe reaction had reported a reluctance to having a second dose.

Dr Anna Goodman, an Infectious Diseases Consultant at Guy's and St Thomas' Hospital in London, advised people to take paracetamol on the morning of vaccination day.

She said: "One thing that is interesting is that people get more symptoms from their first Astra Zeneca dose and their second Pfizer dose.

"We aren't sure why that's happening."

Professor Phil Spector, Professor of Genetic Epidemiology at King's College London, said there was also some evidence that certain drugs, including steroids,taken by patients with underlying health conditions were the same used to treat the virus, which may have offered some protection to those patients.

He said the Medicines and Healthcare products Regulatory Agency (MHRA) was carefully studying data on more reactions to vaccines and stressed that around 80% of people will not experience any side-effects.

He added: "So far, there is no evidence in any country- and American is looking at this quite closely - that the amounts of severe problems is more than you would expect."