“The reports suggest that common adverse reactions to mRNA vaccines, such as fever and nausea, may have contributed to a fatal outcome in some frail patients”, says Sigurd Hortemo, chief physician at the Norwegian Medicines Agency.

In a press release, the Norwegian Medicines Agency stated that as of 14 January, there had been 23 reported deaths that occurred shortly after receiving the Covid-19 vaccine.

Of those deaths, 13 have been assessed which concluded that side effects associated with the vaccine may have contributed to severe reactions among the frail and elderly.

As a result, the National Institute of Public Health has updated its Covid-19 vaccination guide with more detailed advice on vaccinating the elderly who are frail.

“All deaths that occur within the first few days of vaccination are carefully assessed. We cannot rule out that adverse reactions to the vaccine occurring within the first days following vaccination (such as fever and nausea) may contribute to more serious course and fatal outcome in patients with severe underlying disease,” the agency says.

However, the agency also noted that in the country’s vaccination campaign for elderly individuals, many of whom are in nursing homes with serious underlying conditions, “it is expected that deaths close to the time vaccination may occur.” 

According to the agency, an average of 400 Norwegians die each week in nursing homes and long-term care facilities. 

“For those with the most severe frailty, even relatively mild vaccine side effects can have serious consequences,” the Norwegian Institute of Public Health says, according to Bloomberg. “For those who have a very short remaining life span anyway, the benefit of the vaccine may be marginal or irrelevant.”

Vaccinations programmes have started to be rolled out across the world to combat the coronavirus, which has killed nearly 2 million worldwide according to data compiled by John Hopkins University.

Norway's vaccine warning is the most cautious statement yet from a European health authority. T

he Norwegian Medicines Agency noted that the large studies on Comirnaty (BioNTec/Pfizer) did not include patients with unstable or acute illness – and included few participants over 85 years of age.

According to Bloomberg, Pfizer said in an e-mailed statement that they and BioNTech are working with the Norwegian regulator to investigate the deaths in Norway. 

Last week, the U.S. Centers for Disease Control and Prevention (CDC) announced that allergic reactions to COVID-19 vaccinations are relatively rare. The CDC said that of nearly 2 million people who were vaccinated against COVID-19 during a 10-day period in December, only 21 people experienced severe allergic reactions. 

The agency added that most of those people had a history of allergies or allergic reactions, and for the 20 people the CDC followed up with, all had recovered and been sent home.

The first Europe-wide safety report on the Pfizer-BioNTech vaccine will probably be published at the end of January, the regulator’s key medicines committee said Friday, according to Bloomberg. Vaccine makers are required to submit data monthly.