The World Health Organisation (WHO) is studying data from Sweden and Denmark about a possible link between the use of the Moderna Coronavirus vaccine and rare side effects.

The study also is for an increased risk of heart inflammation, WHO Assistant Director-General for Access to Medicines, Vaccines and Pharmaceuticals Mariangela Simao said on Thursday.

“WHO is currently looking at the decision in Sweden, in Denmark to stop vaccinating with the Moderna vaccine.

“So we shall be seeing a statement of the global advisory group on vaccine safety in the next few days,’’ Simao said.

Sweden and Denmark had in the first week of October said they will pause the use of Moderna’s COVID-19 vaccine for younger age groups after reports of possible rare side effects, such as myocarditis.

The Swedish health agency said it would pause using the shot for people born in 1991 and after as data pointed to an increase of myocarditis and pericarditis among youths and young adults that had been vaccinated. Those conditions involve an inflammation of the heart or its lining.

“The connection is especially clear when it comes to Moderna’s vaccine Spikevax, especially after the second dose,” the health agency said in a statement, adding the risk of being affected was very small.

Anders Tegnell, Sweden’s chief epidemiologist, said the health agency would continue to “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 the disease.

In Denmark, people under the age of 18 will not be offered the Moderna vaccine out of precaution, the Danish Health Authority said.

It said that data, collected from four Nordic countries, shows there is a suspicion of an increased risk of heart inflammation when vaccinated with Moderna shots, although the number of cases of heart inflammation remains very low.

The preliminary data from the Nordic study have been sent to the European Medicines Agency’s (EMA) adverse reaction committee and will now be assessed.

Sweden and Denmark said they now recommended the Comirnaty vaccine, from Pfizer/BioNTech, instead.

Norway already recommends the Cominarty vaccine to minors and said that it was reiterating this, underlining that the rare side effects may be more frequent for boys and young men, and mainly after receiving a second dose.

“Men under the age of 30 should also consider choosing Cominarty when they get vaccinated,” Geir Bukholm, head of infection control at the Norwegian Institute of Publica Health, said in a statement.

A Finnish health official said Finland expected to publish a decision on Thursday.

The EMA approved the use of Comirnaty in May, while Spikevax was given the nod for children over 12 years old in July.

Additional reports from Aljazeera.com