According to a Bloomberg report, 13 autopsy results have indicated that the common side effects may have triggered severe reactions in frail, elderly people leading to their death, said the Norwegian Medicines Agency.

"For those with the most severe frailty, even relatively mild vaccine side effects can have serious consequences," the Norwegian Institute of Public Health was quoted as saying in the report.

"For those who have a very short remaining life span anyway, the benefit of the vaccine may be marginal or irrelevant," it added.

This does not mean that the younger healthier individuals should avoid the vaccine. The deaths tell what the countries should watch out as they begin to issue safety monitoring reports,

European Medicines Agency has said tracking the safety of coronavirus vaccines, especially those using the new technologies like RNA, will be the most challenging, said the report.

Pfizer and BioNTech are working with the Norwegian regulator to investigate the deaths, the report stated, adding that the agency found that the number of deaths are not alarming and in line with the expectations.