Vaccine side effects: What are the possible side effects from Pfizer, AstraZeneca and Moderna vaccines?

With over three quarters of the Scottish population having now had their first dose of the vaccine, here’s what you need to know about what sort of side effects to expect and how they differ.

87% of over 18-year-olds in Scotland are now covered by their first dose according to Public Health Scotland’s daily coronavirus data, which also shows that around over two thirds of the population have recently received their second dose.

But as more people are called to attend drop-in vaccination clinics in Scotland following the Delta variant’s rapid rise and a new variant of interest being watched closely by the World Health Organisation, some are also experiencing the mild side effects of the vaccine – which appear to differ depending on dose and type of vaccine.

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The vast majority of the UK's adult population have no had at least one dose of a Covid vaccine. Picture: JPIMEDIA

Before we continue let’s be clear: get the vaccine if it’s offered to you.

It is the best method we have of keeping people safe from Covid-19.

Currently, AstraZeneca, Moderna and Pfizer are the only vaccines approved for use in Scotland’s vaccination programme.

Across all three, the most common side effects tend to be weak and short-lived, with side effects such as having a sore arm from the injection, feeling tired and achy or having a headache and nausea.

Covid after vaccine: What are the possible side effects after Pfizer, AstraZeneca and Moderna vaccines? (Image credit: Tero Visalainen via Getty)

In some cases, people have experienced a flu-like reaction to the vaccine in feeling feverish and dizzy but scientists have warned that this should not be confused with getting covid-19 as a result of the vaccine.

There are some serious, but very rare, side effects to also watch out for.

The UK Government and its medicines regulator, the Medicines and Healthcare products Regulatory Agency (MHRA), has now listed heart inflammation as a possible side effect of the Pfizer and Moderna vaccines.

Having updated the product information for both vaccines to include myocarditis and pericarditis, the government has stressed that the side effect is extremely rare and has been very mild when occurring in patients, with most recovering quickly after treatment.

Another, perhaps overlooked, form of side effects have been identified for women, as it emerged this month that over 4,000 women have reported menstrual side effects after receiving a Covid vaccine to the MHRA.

Here’s what you can expect of the side effects for each vaccine:


Side effects from the AstraZeneca vaccine have included the common side effects of: tenderness, pain and bruising at the injection site; feeling unwell, sick or tired; vomiting and diarrhoea; pain in arms and legs; flu-like side effects such as chills, a sore throat, runny nose and high temperature.

Scientists are currently conducting an in-depth study into the vaccine’s links with blood clotting after very rare cases of blood clots were observed in some patients following their AstraZeneca jab.

While stressing the rarity of such instances, the UK Government has said that anyone experiencing symptoms – such as a severe headache that worsens when lying down, bending over, or brings on blurred vision, confusion and drowsiness, as well as any pinprick bruising or bleeding – within four days of having this vaccine should seek immediate medical attention.

Those under the age of 30 are now offered an alternative to the AstraZeneca vaccine in the form of the Pfizer or Moderna vaccine, with those over 40 still receiving this vaccine as the NHS states that the benefits of being vaccinated outweigh any risks of blood clotting for those in this age group.


The Moderna vaccine commonly sees people feeling tired, nauseous or feverish – with vomiting, chills, headaches and muscle aches and stiffness to be expected.

Less common reactions include rashes, redness, hives or temporary sloping of the face on one side (also known as Bell’s Palsy), but this and any facial swelling are rare reactions.

The Government has announced today (July 9) that heart inflammation has now been added as a severe reaction to the Moderna vaccine, with seven reports of myocarditis, six reports of pericarditis and one report of endocarditis following its use up to and including June 30.

The UK Government advises that those experiencing any of these more rare side effects, along with any wheezing, shortness of breath, stomach pain or swelling of the lips, tongue or throat, should try and get medical help as soon as possible.


Like Moderna and AstraZeneca, the Pfizer vaccine is considered to have many of the same, familiar side effects seen above – with pain, redness and swelling around the site of your infection to be expected along with chills, tiredness, headaches, fevers and diarrhoea.

Muscle and joint pain are also among the side effects seen in over one in every ten people.

More rare side effects for the Pfizer vaccine which are likely to affect one in 100 people include enlarged lymph nodes, insomnia, itching around the injection site, feeling unwell or having allergic reactions.

Myocarditis, inflammation of the heart muscle, has been recently identified by the UK Government as a further rare side effect, with 74 reports of myocarditis and 50 of pericarditis (inflammation of the tissue surrounding the heart and holding it in place) following use of the Pfizer/BioNTech vaccine so far.

To find out more about the vaccines and how to watch out for allergic reactions, visit the NHS Inform website at:

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