​​​​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.  

Severe allergic reactions to COVID-19 v​​accines

In a number of European countries, a number of cases of severe allergic reaction, including anaphylaxis, have been reported following vaccination. Such reactions are rare and can occur with all types of vaccination, but are observed more frequently with COVID-19 vaccines than with other vaccines, for example the influenza vaccines. As a result, Norwegian and European medicines authorities are closely monitoring the situation. 
Norway has reported 45 cases of suspected anaphylactic reactions as adverse reactions after vaccination of persons aged from 20 to 92. The 45 cases comprised 38 women and seven men. 30 cases have been reported with the Comirnaty (Pfizer) vaccine, 12 with the Vaxzevria (AstraZeneca) vaccine and three with the Moderna vaccine. All the patients had recovered or were recovering when the reports were issued. 

Severe allergic reactions usually develop rapidly after vaccination, and require immediate treatment as they can be life-threatening. Preparedness for anaphylaxis is a requirement at all vaccination sites. Health professionals must follow the Vaccination Guide issued by the Norwegian Institute of Public Health (FHI).

Reports of blood clots and low blood platelet counts 

The incidence of blood clots increases with age, and low blood platelet counts are associated with many chronic diseases, but it is rare for them to occur in combination. At the time of writing, there have been seven confirmed cases of rare but severe blood clots with a low blood platelet count and bleeding after vaccination with the viral-vector based vaccine, Vaxzevria (AstraZeneca), of which four have been fatal. 

We have assessed four reports describing different forms of blood clots where the patient has simultaneously been diagnosed with a low blood platelet count after vaccination with the mRNA vaccine. We believe there are several possible causes to explain these symptoms in these patients. 

“It is our assessment that these cases do not represent the same clinical picture identified after vaccination with Vaxzevria. All the patients involved are older, have one or more underlying conditions or take medicines that increase the risk of blood clots and low blood platelet counts,” explains consultant Sigurd Hortemo.

​Distribution of reported adverse reactions by age

We receive more reports of adverse reactions from younger patients who have been vaccinated than from older patients, even though the number of older persons vaccinated is much higher so far. To date, adults under the age of 60 who have been vaccinated are primarily health professionals and persons with an increased risk due to underlying conditions.  Studies of the vaccines have also produced reports showing a higher number and more significant adverse reactions in younger persons than in older.

​Experience from the influenza vaccine shows us that adverse reactions are more commonly reported in younger adults than in older adults. This can be attributed to a number of factors, including the fact that younger people have a stronger immune response and more noticeable common adverse reactions, or that reports are issued more frequently for younger people in order to clarify whether the reaction is an adverse reaction to the vaccine or not.  “We are also aware that younger people are more likely to report the adverse reactions themselves,” explains consultant Sigurd Hortemo.

Reports of serious adverse reactions

 Classifying an adverse reaction as serious does not necessarily mean that the condition is medically serious.  Certain incidents (for example, if the patient faints) shall always be classified as serious.  The same also applies to hospitalisation, including both patients who are admitted for short-term observation and who rapidly recover, and patients with permanent injuries and life-threatening illness.  Some conditions are defined as medically significant by the European Medicines Agency (EMA), and are always classified as serious.  The use of joint criteria for classification in Europe enables us to assess reports from different countries holistically. 
The most commonly reported suspected serious adverse reactions in younger patients are fainting, anaphylactic reactions and blood clot conditions. These are included on the EMA’s list.

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. 

The chapter on the coronavirus vaccine in the Vaccination Guide from the Norwegian Institute of Public Health (FHI) has now been updated with a new paragraph: Further vaccination of persons who experienced adverse reactions after the first dose of the coronavirus vaccine.

​​​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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