By NewsDesk  @infectiousdiseasenews

Earlier this week, we reported on Finland restricting the use of Moderna’s Spikevax mRNA COVID-19 vaccine due to Myocarditis risk in some populations.

Finland’s Nordic neighbors-Sweden and Norway- have taken a similar course concerning the vaccine.


Image/Robert Herriman

The Swedish Public Health Agency has decided to suspend the use of Moderna’s vaccine Spikevax, for everyone born in 1991 and later, for precautionary reasons. The cause is signals of an increased risk of side effects such as inflammation of the heart muscle or heart sac. However, the risk of being affected is very small.

Myocarditis (pericarditis) and pericarditis usually go away on their own, but the symptoms need to be assessed by a doctor. The conditions are most common among young men, in connection with, for example, viral infections such as covid-19. In 2019, approximately 300 people under the age of 30 were treated in hospital with myocarditis.

Data point to an increased incidence also in connection with vaccination against covid-19, mainly in adolescents and young adults and mainly in boys and men. For the individual, the risk of being affected is very small, it is a very rare side effect.

New preliminary analyzes from Swedish and Nordic data sources indicate that the connection is especially clear when it comes to Moderna’s vaccine Spikevax, especially after the second dose. The increase in risk is seen within four weeks after the vaccination, mainly within the first two weeks.

The Swedish Public Health Agency has decided to recommend a break for all use of Spikevax for people born in 1991 and later. The decision is valid until 1 December 2021. The Swedish Public Health Agency will return with a notice of recommendation after this date.

– We follow the situation closely and act quickly to ensure that vaccinations against covid-19 are always as safe as possible and at the same time provide effective protection against covid-19, says Anders Tegnell, head of department and state epidemiologist at the Swedish Public Health Agency.

People born in 1991 and later who have received a dose of Moderna’s vaccine will not be offered a second dose of covid-19 vaccine at present, discussions are ongoing about the best solution for that group. In total, there are about 81,000 people.

For people born in 1991 who have not previously been vaccinated, the Pfizer/ Biontech Comirnaty vaccine is recommended as the first and second dose.

– Those who have been vaccinated recently, with their first or second dose of Moderna’s vaccine, do not have to worry about the risk is very small, but it is good to know what symptoms you need to be vigilant about, says Anders Tegnell.

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Both myocarditis and pericarditis often go away on their own, without causing any lasting problems, but suspicious symptoms should be assessed by a doctor at, for example, a health center or emergency room. Medical treatment and monitoring in hospital may be needed in established cases.

Symptoms of myocarditis and / or pericarditis include:

  • Fatigue and shortness of breath
  • Irregular heartbeat and palpitations
  • Fever and pain in the body
  • A feeling of pressure or weight over the chest
  • It hurts to breathe deeply
  • Pain in the left or middle of the chest


Norway’s FHI is re-emphasizing the recommendation that young people under the age of 18 who are to be vaccinated are offered Comirnaty regardless of which mRNA vaccine they received as the first dose. Men under the age of 30 should also consider choosing Comirnaty when they are to be vaccinated, says Geir Bukholm, director of infection control at the Norwegian Institute of Public Health.

Surveillance analyzes of reported adverse reactions from the USA have suggested that myocarditis may be more frequent when using Moderna’s vaccine as a different dose than the BioNTech / Pfizer vaccine, but the numbers have been small and therefore uncertain. New monitoring data from Ontario, Canada, confirm that this observation is correct, and preliminary monitoring data from Norway, Sweden and other countries may indicate the same. 

The most common cause of myocarditis is viral infections, and a seasonal variation is seen where it occurs more often in late summer and autumn than at other times of the year. Myocarditis is most common in young men and boys. An increased incidence of myocarditis has been seen after the use of mRNA vaccines, and here too it is more common in young men and boys. Most people who have been affected by the rare side effect of myocarditis after vaccination have had relatively mild symptoms and the people have recovered quickly with ordinary treatment of the disease.  

Background for advice

Norway is collaborating with the other Nordic countries on health register analyzes to detect and investigate rare side effects. An overall basis of figures from all the Nordic countries gives strength to the analyzes. The Nordic registry study looking at the incidence of myocarditis and pericarditis has not been completed, and therefore has not yet been published and final conclusions can not yet be drawn from this study. Norwegian monitoring data included in the Nordic register study indicate an increased incidence after Moderna as the second dose. The Norwegian Institute of Public Health is therefore now issuing a clarification of the advice not to give Spikevax to those under 18 years of age, and that men under 30 years of age should consider choosing Comirnaty, as a precautionary principle. The same has been done in Sweden .      

However, the side effect is rare and the absolute risk is still low Both of the two mRNA vaccines used in the Norwegian coronary vaccination program are good and very effective, and provide a high degree of protection against severe covid-19 infection Spikevax from Moderna seems to provide somewhat better protection than Comirnaty from BioNTech / Pfizer against disease caused by the delta variant (updated October 7, removed “mild and severe” before disease). 

– Those who are to be vaccinated in the future can in any case choose the type of vaccine they want, both as the first and second dose, Bukholm continues. It is important to emphasize that Spikevax from Moderna is as effective a vaccine against covid-19 as Comirnaty, and both types of vaccine are still recommended for those over 30 years of age. 

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The recommendation that Comirnaty should be used for everyone under the age of 18 has already been given Children and adolescents under the age of 18 have previously been recommended to Comirnaty as there is greater experience with the use of this vaccine in the age group, in line with the precautionary principle . The knowledge that myocarditis can occur more often after using Spikevax than Comirnaty, also in somewhat older age groups, strengthens the previous assessment .

FHI therefore emphasizes the recommendation that children and young people aged 12 to 17 should still be offered Comirnaty and not Spikevax. Those under the age of 18 who have received the first dose of Spikevax should also receive the second dose of Comirnaty .    This applies to approximately 3,500 young people born in 2004 and 2005 who have received Spikevax (4% of those vaccinated), the rest have received Comirnaty.

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