Side effects or symptoms after vaccination
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COVID-19 vaccines can cause side effects, but they are mostly mild or moderate, and pass after a few days. For some, the symptoms will be more severe. Side effects from the vaccines are being closely monitored.
From autumn 2023, only the updated variant vaccine Comirnaty Omicron XBB.1.5 (BioNTech/Pfizer) is used in the Norwegian coronavirus immunisation programme. The following vaccines have been offered in the immunisation programme in the past:
- Spikevax (Moderna)
- Nuvaxovid (Novavax)
- Vaxzevria (AstraZeneca): the vaccine was withdrawn from the Norwegian immunisation programme in May 2021
Another vaccine was available outside the programme for a shorter period: Jcovden (Janssen).
The coronavirus vaccines may cause side effects among many of those vaccinated, but they are mostly mild / moderate and pass after a few days. For some, the symptoms may be more severe. The mRNA vaccines appear to cause more of the common side effects than other vaccines. Nuvaxovid generally gave slightly milder side effects with a shorter duration than the mRNA vaccines.
The side effects usually occur during the first 1-2 days after vaccination. Common side effects are pain and swelling at the injection site, fatigue, headache, muscle pain, chills, joint pain and fever. Allergic reactions occur in some people. There is good knowledge of common side effects after vaccination, but new rare side effects cannot be ruled out.
Among the rarer side effects reported after the mRNA vaccines and Nuvaxovid are inflammation of the heart muscle (myocarditis) and inflammation of the pericardial sac (pericarditis). The condition causes chest pain, shortness of breath, palpitations, and fever. In the event of such symptoms, consult a doctor. The condition most often occurs among adolescents and young adults and symptoms usually appear within two weeks of vaccination. A Nordic study has shown that myocarditis occurs somewhat more often after the use of Spikevax (Moderna) than after Comirnaty (BioNTech/Pfizer). The NIPH has therefore recommended that people under the age of 30 receive Comirnaty rather than Spikevax.
Many have reported menstrual disturbances after the corona vaccine. The Norwegian Institute of Public Health uses population surveys to obtain answers about whether there may be a connection between the corona vaccines and these symptoms. The first results from these investigations showed that more people reported heavier menstrual bleeding after vaccination with the corona vaccine, and heavy menstrual bleeding has since been listed as a possible side effect in the product information of the mRNA vaccines.
When large parts of the population are vaccinated, many will experience common diseases and complaints in the period after vaccination. Symptoms that occur in the period after vaccination are not always due to the vaccine. Vaccine side effects can sometimes be difficult to distinguish from symptoms of infections or other diseases. If you experience unexpected, severe or prolonged symptoms after vaccination, you should contact your doctor or other healthcare professional for assessment and advice. Healthcare professionals have a duty to report serious or unknown reactions that they suspect are due to a vaccine. You can also send a message via the form via helsenorge.no.
Follow-up of side effects
When vaccines are developed, the goal is always for vaccines to give the best possible effect with the fewest possible side effects. Even if the new vaccines are tested thoroughly, rare side effects cannot be ruled out. Some side effects are only discovered when vaccines are in wider use and have been given to many more people and to more varied groups than in the studies.
After the vaccines are in use, the Directorate for Medical Products (DMP), together with the NIPH, will monitor closely whether any unexpected side effects arise. There is also extensive international collaboration with the other countries that use the same vaccines. In addition, the vaccine manufacturers are required to conduct new systematic safety studies.
The NIPH processes vaccine side effects reported by healthcare personnel and the Directorate for Medical Products (DMP) processes reports from citizens. All reports are collected in the Side Effects Register at DMP. Since January 2021, the Directorate for Medical Products has regularly published reports with an overview of reports of suspected side effects after vaccination in Norway.
It can be difficult to assess whether an event after vaccination is due to the vaccine, or whether it coincidentally occurred in a close time context. It is therefore important to contact a doctor in case of concerning symptoms, so that an illness requiring treatment is not overlooked. It can be difficult to conclude with certainty whether an event is due to a vaccine or to chance based on one or a few individual events.
Long-term effects and delayed side effects
More than 13 million doses have been administered in Norway, and almost 14 billion doses globally. This provides good insight and knowledge about side effects after coronavirus vaccination.
Uncommon with side effects later than 6 weeks after vaccination
For coronavirus vaccines and other vaccines, side effects usually occur in the first few days and within the first two weeks after vaccination. Most vaccine side effects are transient and last for a few days (1-3 days). In rare cases, long-term side effects lasting more than 3 months may occur.
It is very unusual for side effects to occur more than 6 weeks after vaccination.
This knowledge is based on side effect monitoring over several decades and data from the use of many different vaccines worldwide. Every year since 1952, hundreds of thousands of vaccine doses have been given through the Norwegian child vaccination programme. In addition, a large proportion of the population receives an annual influenza vaccine, and adults are recommended regular booster doses of several vaccines.
Of all the vaccines and vaccine types given in Norway, only one vaccine was registered with a serious side effect more than 6 weeks after vaccination. Pandemrix was offered during the swine influenza pandemic in 2009/2010 where some children and adolescents developed narcolepsy after vaccination. 700,000 people under the age of 30 were vaccinated with Pandemrix and 56 were diagnosed with narcolepsy. 60,000 in the same age group were registered as having influenza disease and 16 of the unvaccinated group also developed narcolepsy.
Clinical study participants monitored
When new vaccines are developed, large clinical trials are conducted with many thousands of people, with strict international requirements. Clinical studies give us good knowledge about the most common side effects.
Vaccine manufacturers are also required to follow up the study participants for a minimum of one year after vaccination to give the global community more knowledge about the effect of the vaccine and to detect any long-term side effects.
Suspected new side effects
Suspicion about new side effects can come from different sources - for example, by the public and healthcare personnel reporting suspected side effects, so-called spontaneous reporting, or by researchers publishing new knowledge in peer-reviewed medical journals.
The Directorate for Medical Products (DMP) monitors side effect signals in Norway, and the NIPH assists in the work.
An extensive international collaboration identifies potential new side effects and follows up any signals received. The signals must be investigated before they can be assessed for a possible causal association with vaccination or not, and this must be both thorough and timely. As a rule, little will be known about what triggers a possible new side effect, when and how often they occur, and whether some groups are more at risk of side effects than others. This is something that the most important studies try to identify.
It is very important to be able to compare the incidence of a possible side effect among those who have and who have not received vaccines. However, since many people in Norway have now received a coronavirus vaccine, it is not so easy to compare vaccinated against unvaccinated. Good health registry data and studies are essential to be able to compare the common incidence of various diseases in the population before and after coronavirus vaccination began.
Good health registries and collaboration allow quick response
Access to reliable health data in the NIPH's emergency preparedness registry Beredt C19 has given us new opportunities to study signals about side effects, and monitor changes in the incidence of various diseases in the population. If many cases of a particular condition are reported after vaccination, it will be possible to quickly investigate using health registry data whether the number of cases of the condition is higher among those who have received the vaccine than usual. The preparedness register is a temporary register that was established in connection with the pandemic, and the information must be deleted when the pandemic is over and evaluated (provisional deletion date for the information is 30.06.2024)
The NIPH collaborates with other Nordic countries on studies of signals to obtain a larger, common statistical basis. In this way, the possibility of detecting any changes in the occurrence of rare side effects is increased. Compilation of data from national health registries in several Nordic countries has been important in the investigation of rare, suspected side effects after coronavirus vaccination.
Stopped AstraZeneca vaccine
An example of this working well was when vaccination with Vaxzevria (AstraZeneca) was suspended in March 2021. After the first notifications of a serious condition with blood clots, low platelet count and bleeding (VITT), health registry data from Norway and Denmark were compiled. This showed an increased risk of a serious and unusual blood clot condition in the brains of vaccinated people compared to those who were not vaccinated. Vaxzevria was permanently removed from the Norwegian coronavirus immunisation programme in May 2021 as a result of these side effects.
Large ongoing population surveys provide important insights
In Norway, signals are also followed about other symptoms or diagnoses that are not captured in the health registry data because a comprehensive diagnosis code is missing or the patient has not consulted the health service. NIPH does this through large population surveys (cohort studies).
When the signal about menstrual disorders appeared in the spontaneous reporting system of the Directorate for Medical Products, questions about menstruation were quickly included in these studies for female participants. The first results from the studies show that coronavirus vaccination can affect menstruation in young women 18-30 years.
After a review of available data, including reported side effect reports from European countries, clinical trials and publications, heavy menstrual bleeding was listed as a possible side effect with an unknown frequency in the summary of product characteristics (SmPC) and package insert of Comirnaty (BioNTech/Pfizer) and Spikevax (Moderna) in October 2022.
Results from analyses have been published later showing a connection between corona vaccination and bleeding disorders in other age groups. There have been reports of unexpected abdominal bleeding after corona vaccination among women who have stopped menstruating due to menopause or because they use hormonal preparations. Follow-up is still ongoing. Whether the pharmaceutical authorities will consider unexpected bleeding in women who do not menstruate as a possible side effect, and include this in the product information, has not been decided.
Data have also been collected on other symptoms, including persistent headaches, fatigue and worsening of chronic diseases. Analyses of the data collected in the cohort studies are ongoing, and it is too early to comment on a possible connection with vaccination.
Number of adverse reaction reports expected to increase
With such a large proportion of vaccinated people in the population, reports of symptoms or conditions with a suspected association with the vaccine will be received for a long time to come. This is a natural consequence of the notification system.
Any suspected link between an incident and vaccination should be reported to identify possible side effects that can then be investigated further. Reports of suspected side effects provide useful knowledge about the vaccines and are important to provide sound vaccination advice. The aim of a vaccine is always to give the best possible effect with the fewest possible side effects.
The NIPH considers that the benefit of the vaccines we use in Norway (protection against severe COVID-19 disease course) is much greater than the risk of serious vaccine side effects. Our assessments are based on the latest available knowledge about the vaccines and about COVID-19 disease.
The health authorities continue to monitor the situation closely both in Norway and the rest of the world. Even after thorough studies prior to approval, we can never guarantee that rare side effects will not occur when vaccines are used on large population groups. Any new signals or suspected side effects that appear that may be related to the vaccines will be thoroughly investigated.
- Reported suspected adverse reactions of COVID-19 vaccines (Directorate for Medical Products)
