​Reports of serious events are assessed first. The figures therefore do not give a true picture of the distribution between serious and non-serious events. Most of the reports concern common adverse and expected reactions, such as pain at the injection site, headache and general malaise with fever.

Adverse reactions uncovered during studies are specified in the patient information leaflet and the summary of product characteristics. This information is updated if reports are received of new adverse reactions, and when the European Medicines Agency (EMA) decides there is a probable causal link between the vaccine and the adverse reaction.

Click here to go to an overvi​​ew of reports of suspected adverse reactions (the adverse reactions report)

Reaction in the vaccination arm following vaccination with mRNA vaccines

There have been reports of cases of delayed local reaction in the vaccination arm, normally around five to ten days after vaccination. This reaction is sometimes referred to as "COVID arm", with redness and swelling, and in some cases also itching and pain around the injection site. These changes will pass by themselves after four or five days. Data from studies and experience gained during use indicate that this reaction occurs more frequently after vaccination with the Moderna COVID-19 vaccine than after the Comirnaty (BioNTech/Pfizer) vaccine.

There is a risk that the person who is vaccinated will experience the same type of reaction to the next dose. The reaction often occurs more rapidly after the second dose (after about two days), but is rarely as severe. Such reactions are harmless and it is recommended that anyone affected completes the vaccination process by having the second vaccine dose.

Common adverse reactions to vaccines can aggravate existing medical conditions

Infectious diseases and fever are known to aggravate existing medical conditions. For example, the risk of unstable blood sugar levels increases, blood pressure can rise, and the effect of blood-thinning medications such as Marevan can be affected. Similarly, common transient vaccine reactions such as fever, vomiting and diarrhoea can trigger symptoms or aggravate existing medical conditions. As a result, additional checks may be necessary, e.g. in order to measure blood pressure or blood sugar levels, and possibly adjust the dosage of medications.

Common and expected adverse reactions

Most reports of adverse reactions following COVID-19 vaccination, regardless of the type of vaccine used, concern known and transient adverse reactions such as headache, fatigue, malaise, fever, nausea and pain in the body. These usually appear on the first or second day after vaccination and last around two to three days. Most people tolerate these transient adverse reactions well, while others experience significant discomfort during the first few days after vaccination. These suspected adverse reactions are in line with what is described in the product information.

​​How to report adverse reactions

Health professionals are obliged to report suspected serious adverse reactions following vaccination. It is not necessary for the causal relationship to be known; suspicion is sufficient to report an incident. 

It is particularly important to report reactions where any of the following are suspected:

  • new adverse reactions not referred to in the patient information leaflet
  • unexpected adverse reactions
  • serious adverse reactions
  • vaccine failure (severe COVID-19 following full vaccination)

If a person becomes ill with COVID-19 following the completion of vaccination, this is considered a possible vaccine failure. Severe or critical cases (COVID-19 symptoms and disease) in persons who have been fully vaccinated must be reported as a suspected adverse reaction via melde.no.

The general population can report adverse reactions via Helsenorge.no, but you should consult a doctor or other health professional in the case of suspected serious or unexpected adverse reactions following vaccination. You do not need to report a possible adverse reaction yourself if a health professional has already reported the reaction.​ 

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